We are planning a trip to Spain next March for about 3 weeks. We would like to stay in the south of Spain and have a few home bases. We would like to visit Malaga, Granada, Córdoba, Seville and Cadiz. Any other suggestions? We are looking for some advice on our itinerary:
Malaga - 8 nights with day trips to Antequera and
Nerja
Granada - 3 nights
Cordoba- 3 nights
Sevilla- 7 days with days trips

We will be traveling to Portugal from Spain so would it be best to go from SevilleMalaga or from Madrid?

I like that you are giving both Granada and Cordoba 3 nights, and that you are allowing plenty of time for Sevilla. Sounds like a great trip!

For your transportation options, you might spend some time exploring your options on rome2rio.com -- just be sure to link through to the source documents, as the main page is not sensitive to seasonal variation.

Nerja would not bother with. A week in Málaga, for what?
What is you method of transport in Spain?
To get from Spain to Portugal, using public transport, options are limited.
Train from Madrid to Lisbon. Renfe
Bus too https://www.alsa.es/
From Sevilla to Lisbon by bus. Same website as above. or fly.

Would it be better to shorten our stay in Malaga? Would you recommend Cadiz for 3 or 4 days instead?

I asked a question why are you going to Málaga for, what is your answer?

If you want to see the Algarve in Portugal you can take about a 4-hr bus trip between Seville and Faro - but Tavira before Faro was a nice old town with a seaside section too - if going by train and buses Renfe - Spanish Railways site you can book your own long-distance trains at a discount if you book early enough to get those limited in number discounted tickets - ditto for Portugal at www.cp.pt - Portuguese Railways site. www.seat61.com has loads of info on doing that - general info trains and what to expect also www.ricksteves.com and BETS-European Rail Experts.

Another good day trip from Seville goes to Jerez-de-la-Frontera and sherry tours and practice sessions many days of Andalusian horses in local arena.

Based on where you want to visit, and the number of days you have, I would recommend the following itinerary if you are planning on being in Spain during Carnival.

Fly into Málaga (4 nights) with day trips
Bus to Granada (2 nights)
Bus to Córdoba (2 nights)
Train to Sevilla (5 nights) with day trips to Jerez, Cádiz, Sanlúcar de Barrameda, Arcos and possibly Zahara de la Sierra
Bus to Faro (2 nights for beach time)
Train to Lisbon (6 nights) with day trips to Cascais and Sintra
Fly home from Lisbon

But for a trip to Spain and Portugal next March, you should consider being in Cádiz during Carnival which begins on Feb 28 and ends 10 March. It's also big in Madrid and Málaga but Cádiz is considered the best outside of Tenerife. The final night of Carnival in Lisbon will be on March 5 next year.

Friends of ours stayed in Malaga for the month of March and loved the history and the museums. We would enjoy the museums and art galleries. As well, it would be a good home base to visit other places. Malaga would be too big for a day trip so I thought a week would be sufficient. I don’t want to move too many times over the 3 weeks.

We are planning 3 weeks in Spain and possibly 2 weeks in Portugal. Still deciding however...

If you want Museums and the like then Málaga will serve you well.
If you are taking day trips in a car then pick some where away from the city centre for ease of parking.
For me Nerja is more of a British vacation resort. Plus the sea is not worth a dip as it is presently quite polluted.

Bus to Faro (2 nights for beach time)>

Faro ain't on the sea but again Tavira and Lagos are two old neat cities with beaches just out of town. Either of those would be much much nicer cities than Faro or many modern Algarve beach resorts. Can take train Faro to Lagos and bus stops in Tavira I believe before Faro. And in March you may find it too cool even to sit on the beach let alone swim. Avg hi 66:

https://www.holiday-weather.com/faro/averages/march/

I'd also consider stopping in Evora for a few days - really neat old city with lots to see and do - between Algarve and Lisbon or instead of Algarve - bus from Faro and then train or bus to Lisbon. Obidos could be another neat day trip from Lisbon.

Those filling averages do not mean a thing. Weather is unpredictable.

Not again! Yes, weather is unpredictable, but the best single predictor is the average over recent years. For a better sense of what to expect, get information about the average and the variation around that average (e.g., highs and lows).
For data on climate, consult timeanddate.com

For a recent thread on the appropriate use of climate data (and ribeirasacra's misunderstanding thereof) see:
Cadiz and San Sebastian visits and transportation

Yes again weather history websites do not prove anything.
The weather over the past few days
https://www.cope.es/trece/videos/tie...0180926_549404
The average for Málaga.
https://www.holiday-weather.com/malaga/averages/
No comparison.
You accuse me of something you and others have little knowledge of.

Averages are a good indicator of in general what to expect though there can always be divergences - in this case unlikely to be good beach weather. Period.

But averages do not tell you the highs and lows of the weather patten. I do not understand how you do not understand that. There is no way it can be predicted and in fact the Spanish weather agency is not good at even getting a 3 day forecast accurate.

http://www.weatherwizkids.com/weather-climate.htm

IMO, Sevilla was one of my most favorite towns in Spain and would make a good base to see Cordoba and Granada, then Malaga to see Antequera and Nerja. I would not want to spend 1 week in Malaga, I would shorten the stay there and perhaps extend it in another town instead. Dependent on where you are coming from in Portugal, if Lisbon, then perhaps going straight into Sevilla would be best, vs having to go up into Madrid, then come down south. You'll have to research the best connections and route times to determine the most practical route. Have a great trip, Spain is wonderful!

Thank you for your suggestions....we will be going to Spain for 3 weeks before Portugal. I like the idea of Seville for a week. We should probably end there before we head to Portugal. Do you suggest starting in Malaga for 4 or 5 nights? What itinerary do you suggest for the first 2 weeks? I don’t want to move around too much either.

Many here don't cotton to Gibraltar much but I actually loved it - could be a day trip from Malaga - just seeing the Rock is imposing sight and those pesky little tail-less apes - you can climb the rock or take people movers up there. And the town itself is a time trip - kind of an old British town with pubs and greasy cafes and even a large English supermarket last time I was there. If coming by bus weirdly we had to get off on the Spanish side and hoof it across the airport tarmac as buses then and now I think are not allowed by Spain to go into Gibraltar - something about their long spat about sovereignty of The Rock. Anyway for something very weird and different.

Hi kakathy: Malaga is nice but not sure if you want 4-5 days there unless you're making that your base to see those other 2 towns you mentioned. Like PalenQ commented, Gibraltar is a fun diversion. We stayed in Gibraltar for a day/night 1 year ago enroute from Tarifa to Malaga. Indeed, it's a quirky spot of Britain in Spain and yes, you have to stop at La Linea to get into Gibraltar (customs office at "border"). Once in Gibraltar, you can see fabulous views from The Rock over the Strait of Gibraltar into North Africa, etc. The views alone (despite the pesky Barbary apes) were worth our brief sojourn there. You could add Gibraltar to your cities to see around Malaga. Malaga being on the coast is not a direct connection to say, Madrid, so if you are flying into Madrid then it would make sense to go south directly to Sevilla first, then bus (or train) to Malaga. However, if flying into Barcelona, you could take a train down the coast to Malaga and start there, then work your way over to Sevilla. We took only public transportation while we were in Spain and it worked out fine. We saw everything we wanted to see and it was quite convenient. Here's my Spain trip report if you want some additional ideas: Spain, Morocco, Italy trip report w/ teenager