portable gps devices for travel in USA and Spain?

I am looking to buy a portable gps device for car travel in the U.S. and Costa del Sol Spain. How would this work? I will be in Spain 2 weeks only. Is it better to rent (about $10.00 / day in Spain) ? I would rather buy one that can be used here and in Spain.

$10/day times 14 days, you're looking at the cost of a brand new handheld GPS as it is. Even the lower end handhelds will have basic maps of the whole world in them. Many have removable memory cards that you can load street level maps onto for wherever you're travelling to. You don't have to get something as fancy as a TomTom, just pick up a Garmin eTrex and get the Mapsource CD's for the regions of interest. If you have no use for them after your travels, you could always put it up on eBay and sell it for a good amount afterwards. If you buy it on eBay to begin with, it might end up costing you nothing at all if you sell it again after you're done with it!