First of all, welcome to the Land of Milk and Honey!
The weather forecast has been changing (pretty drastically) the past few days but it seems to have settled on 40-80% of rain Thursday thru Sunday. That being said, you should most definitely make some time to float the river.
Two choices to float the San Marcos River:
1.
Lion's Club. They'll hook up you with a tube aand cooler for about $15/person. You put in at City Park (right by campus & Bobcat Ballpark). The float is short (~1-1.5 hours) down to Rio Vista Park but you can float it as many times as you want. A bus will pick you (and your stuff) up and take you back to Lion's Club.
Rio Vista Park
2.
Don's Fish Camp. Google for directions. For about $15/person, Don will take you a few miles up stream in a bus and drop you off and you float back to your car. This float is usually geared less towards families and more towards college students.
SM River near Don's
You can also go down and float in New Braunfels:
1.
Comal River. Rent from one of the river outfitters. I'd recommend Texas Tubes because it's right on the river -- good parking, no walking.
Comal River
2.
Guadalupe River. There are 100 different ways to float the Guadalupe but for visitors I'd recommend the Horseshoe. River Sports Tubes on Hwy 306 is good. It's in the middle of the Horseshoe so it's a close walk to the start and a close walk from the end.
Guadalupe @Horseshoe
For San Marcos restaurants, I'd recommend:
-Mexican: Herbert's Taco Hut (get the cheese enchiladas)
-BBQ: Hays County or Black's
-Pizza: Pie Society or Valentino's
-Burgers/Bar Food: Tap Room
-Breakfast: Dos Gatos Kolaches or
-Nice: Root Cellar
Nightlife:
Check out the square (downtown SM). There are ~15 bars with a few blocks around the county courthouse. You'll find one that you guys really like. The only bar off of the square that I'd recommend checking out is Zelick's. Mostly because you're staying right down the street, but also because you might like the upper-20's crowd a little better.
Other things in San Marcos:
If you're interested in these things, go check them out. If I included them on this list, they're worth it...again - only if you're interested.
Cars: Dick's Classic Car Museum - they have a
Tucker 48 with 0.4 miles
Shopping: San Marcos Outlet Malls - two huge outlet malls across the street from each other - literally a mile of outlets
Hiking/Outdoors: Purgatory Creek Natural Area or Spring Lake Preserve - miles and miles of hill country trails
Geology/Caverns: Wonder World - dry cave, formed by an earthquake
Hydrology/Water: Aquarena Glass Bottom Boats - see the springs bubble up from the aquifer that the feed crystal clear San Marcos River
History: LBJ Museum - he was a terrible president, but he belongs to us