You can make good saisons at those temps. Haven't tried it that high with 3711, but its a good versatile yeast thats easy to work with. 565 is the gold standard though. It works at those temps because its basically a wine yeast.
Some good threads here on saisons:
Investing in temp control though is honestly more important than going all grain or even doing full-volume boils. Frankly, if you have that, you can use it for partial chilling as well before you buy/build an immersion chiller or counterflow/inline.
I knew a guy that was able to order the parts for a home-wired temp controller for around $20, shipped. He found the supplier (somewhere in China) over on Homebrewtalk, but all measurements were in *C, so he kept a printed out chart next to his ferment chest! Then he got an old chest freezer on Craigslist, and the seller ended up trading it to him for some beer, so now he makes amazingly improved beer for around $20 and an hour or so of putting the temp controller together.
If you don't have the initiative/time and have some funds, you can just buy a pre-wired single-stage Johnson controller for $70.
Get temp control and make 'beer' not 'homebrew'!