We will be renting a car in andalucia and wondering if there is such a thing as a bilingual gps in car so we can navigate around?

Do you want bilingual? Or just English? If the latter: yes.

You could always bring your own, if you have bought the European maps for it.

I bought a Garmin on amazon.com a few weeks ago for less than the car rental price for my recent Spain trip, other than not knowing of some construction, it was good...I paid $139 for Garmin Nüvi 270 Gps.

My friend bought the same for his trip to Ireland after I found this price, he is there now so no clue yet on how it worked there for him, but you are asking about Spain anyhow.

Hope that helps.

I would not rely on your GPS as road works or accidents etc can mean diversions. The GPS then goes crazy and simply says turn a around etc. You may have to reprogram it in such an event, a map will help you choose the nearest town. Do not forget that here in Spain the screen cannot block your view of the road, i.e. it must be place either on the dash or just above. Plus the driver must not operate it whilst driving.

My Garmin (without Europen maps, only US and Canada) offers numerous options for the voices--speakers of US, UK, or Australian English, French or Canadian French, etc., plus Swedish, German, Italian, you name it. Play around with your machine and you may find you have more languages than you thought.
I would not be surprised to find a multi-language GPS in European rental cars.

ribeirasacra brings up a good point, buy a Michelin map as backup, it won't help much in the city, but is helpful if diverted on the highway.

you don't need to "read" the GPS screen, the annoying voice will tell you your directions. You can always pull off to recalculate as needed.