We will be arriving in Madrid via Delta (arr. terminal 1) and flying out via Iberia. What is the process for clearing customs and then getting over to terminal 4.

I assume we must claim our luggage upon arrival and go through customs. From that point, do we have to carry it ourselves to terminal 1 or if it is checked through to Porto, do we put it back on a carrosel that will take it to our Iberia flight so that we don't have to handle it until our arrival in Oporto?

Where is the bus at terminal 1? Does it go directly to terminal 1 or is there a loop? If there is a loop, what is the direction of travel (4-3-2-1 or 4-1-2-3)? Approximately how long will it take at 11:30 a.m. on a Monday?

Will we have any trouble with our non-existent spranish?

Were the flights booked totally separately? If not you can probably check your luggage through to Porto.
You go through passport control, then make your way to terminal 4, going through at least one security gate. Just follow the signs.
How much time do you have for the transfer? I always like to look at the airport map so I have a sense of where to go if I have a tight connection.

There is good signage, so not to worry. The inter-terminal bus is easy to find and is marked well. I believe it stops right outside the arrivals hall. It takes awhile to get from Terminal 1 to 4 - you'll swear you are on a bus headed into Madrid - maybe 15 minutes or so.

Thanks yorkshire and november_moon. Our ticket was bought as a though ticket from Atlanta to Oporto - bought at one time. So, does that mean we can forget about checked luggage and just go through passport control?
We do have plenty of time - like 4 hours (enough time for a nap, just joking).

We like good signage and will take your word and not worry.

If all in one ticket in theory they should transfer luggage however, Delta and Iberia are not partners so I'm not sure if they're obligated to do so. Hopefully somebody who has done this type of connection can chime in.
How much connecting time do you have? One time I asked about how much time I should allow between terminal 1 and 4 and was told at least 2 hours. It's about 15-20 mins on the bus.

Sorry, just read your last message and see you have 4 hrs. You should be ok.
You could always call Delta or Iberia and see what they say about luggage transfer.

Yes with 4 hours no worries even if you do have to retrieve luggage, but I would call airline to find out.

Thanks everyone. I will take advice and call both airlines, but will still hope someone has done this before and would have some first hand advice. Happy traveling.