Swamp cooler temp control will do you well at the temperatures you're talking about. My ambient temp is only a touch lower than yours (high 60s to low 70s depending on the season and day), and I can brew a mean Kolsch with a swamp cooler (fermented at 58 and then "lagered" at 40). It's a LOT of work to keep temps that low, but it can be done. But if you want to ferment a beer in the 66-68 range (which will work well for many ales) a couple soda bottles of ice a couple times a day and you'll be in fantastic shape.
Saison and Kolsch are both refreshing, both on the light body end of the spectrum, and both usually have a bit of hop character. I'd say that's where the similarities end. Kolsch is usually paler than Saison (depends on the example, they can be about the same, but most Saisons are a little darker), and a Kolsch is clean with little to no esters, where a Saison really has more esters than any other style. A traditional Saison is definitely a session beer, but most modern ones are quite strong.
I love a good Saison, but you need to be careful with the yeast. Some Saison yeasts are notoriously problematic and love to stall out on you (which also happen to be, in my opinion, the best strains). If you can get Wyeast 3711 French Saison, go with that one for your first. It's a workhouse, very low maintenance compared to other strains, will reliably get the beer to the right level of dryness, and still provides a nice character, it's just not as in your face and complex as other possibilities.