Hi - we live in Cheltenham and in fact will be renting our house out from mid-July in case you are interested!!! It's three bed, three storey town house with a play room, £1,300 pcm.
Where you live very much depends on your budget - Cheltenham house prices are based on school catchment areas. Therefore the expensive areas are Leckhampton, Charlton Kings and Tivoli. The good primary schools include Leckhampton, Naunton Park and our local, St James. The "better" secondary schools are Balcarras and Bourneside, and there is a good grammar school Pates.
The other area with good primary schools, and is cheaper, is Hatherley (Lakeside primary) and Up Hatherley. There are other good schools but not sure what they are called.
The places to avoid are really all up in the north of the town, although once you are up towards Bishops Cleeve it gets better again and the schools are good.
Sorry this may not be a lot of help, I am fairly new to Cheltenham myself (been here less than two years) so don't know that much apart from the area we live in. But let me know if you have any more specific questions.