Well yes there are good and bad needle exchanges.
Needle exchange 1: Carries the size I want, will give me several boxes even without bringing in old ones, is open late and on weekends.
Needle exchange 2: Only has 28g and larger, won't give me more than 3x10packs without old ones, closes at 5, not open weekends.
There's "official policy" and what they actually do, so you really need to find out in person rather than ask on the phone for a lot of issues.
But I used to live somewhere without needle exchanges. For a while I just ordered them online for like $25 for box of 100 BD 31g 1cc 1/2" (public internet store prices are ok right? if not sorry) until I found a cool pharmacist.