> If you like teaching then by all
> means go on to a CELTA but otherwise why spend all that money if you
> discover it's not for you?

Henry is right there, but if you are sure you want to teach (aren't we all?) then the CELTA is the best choice.

To just test the water see if you can volunteer at a local government program, they will probably give you some basic training and send you out to tutor migrants a couple of times a week. I did this in Australia, it was called Migrant Education Program or something similar. I did it to make sure I really DID want to be an English teacher.

Good luck.