Both Karin and Susan have some great suggestions. Renting a space to hold a class before opening one of yours would is a good idea. This way, if there is no traffic (or not enough) coming thru your doors then you’ll know if it’s a good idea for a permanent location. Scouting the other studios would be another way for you to scope your competition. And at the very extreme, maybe you could start teaching classes at these studios to get an inside information and feeling about their customers and the traffic that comes through their doors.
And sometimes you just need to go with your gut feeling…it you have second and third thoughts about it, it’s probably not the right place for you to open your studio :-).