SAT can be done VERY cheap anytime of the yr. There are lots of offerings and it is served by SWA. AUS (45 min away) is served by Frontier who has been offering $29 flights from various places. There is LOTS to do in the region. Wildflowers are a highlight season (but hard to predict precise weeks). And it is crowded in prime areas. (Lodging). I seldom use hotel / motel and often use
Hospitality exchange - Wikitravel $10 / night worldwide, including many excellent stays I have had in Hill Country. TX
Thanksgiving to Christmas is my favorite time in SAT area. Many towns are lit up and have holiday parades, concerts, festivities. Free, Free, and free
This is also a good time to be GONE from Toronto. We had a guest speaker and families from Toronto at our Thanksgiving conference in Comfort, TX only a few weeks ago, they appreciated the temps of 26 c highs and 2 c lows. Plenty of free events and great food.
I wouldn't bother coming in July - Sept, as it might be too unbearably hot to have an enjoyable time. For those months you want to be in BC or PNW USA. (Fresh Salmon and wild berries) (also free). Our hospitality guests enjoy their FREE Alder Smoked Salmon bakes and fresh wild berries for Breakfast.
In TX, you will be getting BBQ brisket for your free dinners.