FN
You dont necesarilly pay for brakes off/brakes on time.Some aircraft are fitted with a hobbs meter that only logs the actual flying time of the aircraft, but you can log all time from brakes off to brakes on. Worth checking with your prospective school. A Busy GA airfield with all the aids is excellent experience.
I trained at Gloucester with 6 runways and full facilities, with quiet airspace for initial training but with plenty of military and busy airspace for X countries and nav experience. Luckily I had the best of both worlds and wasnt paying for taxiing/holding time as a busy Sunday afternoon can be frustrating if you are paying taxi fares and not solid airtime.
If I was learning at a regional Airport i would make sure im on the hobbs and not paying for sitting there aircraft spotting waiting for all the holiday makers to depart.