What would be the ideal tire size/brand for a daily driver? I live in Louisiana, so there is a lot of rain, heat, and bad roads. Money is an object, but I don't really need it to be too cheap. I only just purchased these rims and will not get rid of my stock 17s. I like having a backup.

235/40R18's are your best bet size-wise.

For a good balance of price, performance, and driveability in a summer-only tire, I recommend the Kumho Ecsta SPT - http://www.tirerack.com/tires/tires.jsp?tireMake=Kumho&tireModel=Ecsta+SPT&partnum=34YR8KU31XL&vehicleSearch=false&fromCompare1=yes&place=46

Aren't the 235s a little large to put on a 7" wide tire? Everything I read says they're for rims that are 8"-9.5" wide.

you definitely don't need an 8" rim, I'd probably try to get a 7.5" rim if you haven't bought them yet. However, I think they can jam it onto a 7" rim.

You can get 225's, but your speedometer will read faster than you're actually traveling.

I've already purchased these rims, and I love the way they look on my car. I think I'm going with the 215/40/18s. This lowers my car about 7/16", but I don't think that'll be too much of a problem. If it is, I'll just get the 215/45/18s. They raise the car about 1/16", which is the closest that I can come to the height/radius with 18" rims.