I did my PPL at Cabair Denham/OFT Kissimmee. "Don't pay up front" with them would certainly (IMHO) be valid advice when dealing with them - it was surprising how many extra charges were put onto my account, many of them inflated and in some cases just plain wrong.
However, having just done my hourbuilding at Old Sarum Flying Club, where I paid upfront to get into their discount scheme, I would gladly do the same again, as the accounts are totally transparent, and the scheme worked very well for me. No dodgy dealings there.