My inlaws used to live in San Marcos, my father in law sold the house a few years ago and moved to Temple after my mother in law passed. San Marcos...awesome town...Temple...well...we get to see my father in law. Of course now that he has moved, I see stuff about this site all the time...kills me!
Any way, Austin is a little quicker, little easier, San Antonio isn't a bad option if it is cheaper. If you fly into Austin, stop at El Chile, excellent food, especially the Chili Rellenos. While in San Marcos, you have to make a slight trip to either Coopers BBQ or Kreuz bbq. If you do San Antonio, there is an awesome little car wash, bar, burger place, laundry mat that has awesome burgers. You also have to find some puffy tacos.
If anyone wants a list of stuff to do in Austin/San Marcos, let me know :)