San Antonio City Guide

Which Is Better For A Romantic-get-away: San Antonio, Houston Or Austin?

November 30th will be mine and my girlfriend’s 3 year anniversary and I got some great deals on Southwest Airlines to surprise her with her first plane ride to either one of these three cities: San Antonio, Houston and Austin.
We will get there on the 25th of November and leave on the 30th (staying through Thanksgiving) and I need to know which of these cities will best supply the following:
1) Night life (I’m 21, but she’s only 19)
2) Fall Events (which looks, acts, feels better in autumn)
3) Distance (I can’t rent a car so we’ll be walking mostly, public transportation or pedestrian friendliness will help a lot)
4) Outdoors (kayaking, sites/scenery, ect.)
5) Romantic Venues (it is our 3 year anniversary most marriages don’t make it that long)
6) Places to Shop (malls, markets, ect.)
7) Arts (galleries, concerts/performance halls, ect.)
8) Affordable (this is all out of my part-time $9 per hour worker/full-time college student’s pocket)
9) Safety & Cleanliness
10) Atmosphere
11) Places to Crash (prefer more affordable than high quality)
I am a Student, as is she, so any student deals or benefits would be most welcome. Please mention anything I may have forgotten and be hasty please; I have to purchase the plane tickets by midnight tonight.
Thank you soooooooo much for your help!!