I've rented from condo owners through Redweek before a few times, and always had a good experience. Since it looks like you're going in May(?) that is good since it's before most schools are out. It's only like $15 or so for a year membership to Redweek so for me it's been worth it. If you go that route, I think you're always going to be safe sticking with one of the larger companies like Marriott, Hilton, and Sheraton (Starwood). We own a Marriott timeshare, so always stick with them (to get our points and nights, etc...).
Also, if you have any close friends that own timeshares and have membership with Interval International, they can look for you for "getaways" - these are prepaid weeks (basically extra inventory) that they can put in your name for an extra fee. I've used those many times for Orlando timeshares (like Marriott's Grand Vista, Harbor Lake, and Sabal Palms two bedroom units each time for less than $400 for a week - huge money saver!).
I believe RCI has the same type of deals too.
I find we save by staying in a condo, so we pack less (do laundry daily), eat in a lot (healthier too) and we get along better with more space!
It's free to browse Redweek, but you have to join to contact someone about a rental.