I presume you're talking about an ale, which in that case you should be OK with fermentation (not ambient temp, but the actual fermentation temp in the bucket) going to 76F roughly. I haven't done a secondary yet (will be doing one in 1.5 weeks), but from what I read 70F - 78F even is OK. Any higher than that and you're bordering on creating off tastes, etc.
I would get a Gott cooler (or just a big plastic bucket), fill it with water maybe 1/3 - 1/5 way up the pail / carboy and rotate some frozen 1Q water bottles daily. I currently do that in the bathtub for my 2 primary's that are fermenting, with water to the 2gal mark and 5 1Q frozen bottles in the morning and at night, and temps are at 68F - 70F in San Diego. Just two weeks ago on my last batch, without the tub, temps were up to 79F.