To add, the trip is planned for early march next year..

It will be very difficult to explore both areas from one base, and finding anything half-way decent for less than €100/night will be tricky. You can check Villa de Abalos (www.hotelvilladeabalos.com) in the Rioja or some of the accommodations in Laguardia.

Hotels in the Ribera del Duero are in short supply, but you can check out the hotels in Peñafiel, Pesquera de Duero, and those in or near Aranda de Duero. There are a few nice wine hotels in the Ribera del Duero, but they are well beyond your budget.

As far as visiting any of the bodegas in either the Rioja or the Ribera, you'll need reservations in advance. And you can forget about visiting Vega Sicilia or Pingus. They are not open to the public, besides, Pingus in nothing more than a warehouse in Pesquera de Duero. The owner, Peter Sisseck, the flying winemaker, is only there when he needs to bottle a few bottles of wine for his customers, or is doing a private tasting for some of them.

For a little more information, you might want to check out the following newsletter from Feb 2011: www.iberiantraveler.com/Ribera_del_Duero_Wine_Region.pdf

And don't forget to check Maribel's Guide to the Rioja for information on visiting the area.

I can't speak to the Ribera del Duero region, but if you're only going to visit La Rioja for 1-2 days you'll be hard pressed to visit more than 3-4 bodegas. Generally you can visit one in the morning (and in some cases squeeze in 2 morning visits) and then one in the afternoon especially if you're looking for an English tour. Most bodegas aren't set up for mass tourism so the tours aren't on coordinated schedules. In September I was able to visit 3 bodegas in one day (2 in the morning and one after lunch) but this was a first for me and frankly it was a bit too much). You definately need to book in advance.

@Robert2533 could you let me know what are some of the nice wine hotels u mentioned?
@CathyM any wineries I'm la Rioja to recommend? There's too many!! Thinking of spending 2 nights in Ribera del duero and then driving down to la Rioja for 2 nights. Feasible? Suggested routes?

You ask if the trip is doable, but give little details of your plans.
Is this trip included in the trip you ask about here?
http://www.fodors.com/community/europe/2-wks-spain-febmar-barcelonasevillemadrid-vineyards.cfm
If so I can see some one has suggested that For a solo traveler driving can be tedious without having someone to talk to or share driving time I would concur with this. However seeing that a trip between Burgos and Haro is around an hour it is easily doable. But if you whole trip is solo in a car then please take in the advice given in you other thread.