Which Spanish city to pick?
We have not heard from OP in almost three weeks, so this may be more for the eyes of other (future) forum visitors.
To amplify Mushroom's excellent point: Over the years I have found that it takes quite some logistics gymnastics to make the most of one's investment in vacation time and money in Spain.
Daytrips only really work if you can get up and out in time to arrive between 8 and 9, and consider the day done by 2 or so when siesta time rolls around. If you don't want to get caught in the quandary of what to do and where to go after a long sit-down restaurant lunch, better buy provisions before, say, 1PM and get out of town, eating on the train or stopping your car in a shady spot.
The best way I've found is not to stay put in one town or city (except, of course, while you explore that town or city and can find siesta refuge in your room), but to use the siesta hours to drive to a new place, check in by late afternoon, rest and freshen up, check out the surroundings of the hotel or visit a museum nearby (probably open til 8 or9 PM), thus work up an appetite, join the dinner crowd around 10PM, and sightsee this new town the next morning. If you won't be staying another night, then ask for your bags to be held after check-out in the morning, it is always graciously done and a tip is in order, of course.