First of all, KUDOS to you for asking questions first and not just breeding without any concept of what you're doing. You are finding that you'll get very honest opinions on this forum - sometimes blunt, but the information you're receiving is going to really help you.
Unfortunately, just the fact that your girl is registered through ACA probably means that she is not really breeding potential if you're wanting to do things right. The reasons that "breeders" choose to use registries like ACA is that they either using stock that isn't registered through a more reputable registry, or that they're using stock that isn't registered at ALL and they may not even know the backgrounds. There are a few of these "fake" registries that allow pretty much anything - even to the point of just accepting a person's word that the pedigree they supply is valid. Breeders who use these registries can and sometimes do just make up a pedigree, so you have no true way of knowing if anything on your dog's pedigree is true.
One of the big things in breeding is health. ALL good breeders have a huge focus on trying to eradicate and/or avoid genetic health problems in their chosen breed. If you were going to breed JRT's or PRT's, you would want to x-ray hips and elbows (through an established organization like Orthopedic Foundation of Animals or OVC, PennHip, etc.). You'd also want patellas checked, as well as thryoid (hypothyroidism appears to be more of a problem in these dogs that I would have thought). And, of course, the BAER hearing test is vitally important.
And just as important is the health of the parents and grandparents of your breeding dog. This is one of the places where it's so important to know what the true pedigree is. YOUR dog may be apparently healthy but be carrying genes for various health problems that just happen to be skipping her generation. Because of this, knowing what kind of health background her relatives had is extremely important.
The same goes for the conformation and working ability. What kind of background does she have - pedigree-wise - in championships and working titles? With an ACA pedigree you just really can't know, because anything listed could be completely false.
I would highly recommend that you choose to make this girl your learning experience. Study up on showing, attend shows, see what it's all about and talk to people (not just JRT people, but other breed people too). Have her spayed, get your ILP (indefinite listing privilege) through AKC and then show her in obedience, rally, agility, tracking, earthdog, etc. EVERY show/trial will be a learning experience and you will gain a certain cameraderie with the other dog people. Tell them that you thought of breeding and then researched and realized that a dog with an ACA registry isn't really a good way to breed, and that instead you had her spayed and you're on a quest to learn all you can before you get your next JRT or PRT. This will impress people .. believe me, dog show people/breeders see all SORTS of people who make the wrong decision, and you will look OH so good when you show them that you made the right decision.
I started off, nearly two decades ago, with purebred but non-registered dogs. I didn't know jacksh*t at the time and might have bred one of mine if I hadn't started into shows and been "educated" by others. And now I've put titles on six dogs (more than 30 performance titles) and I finally have a bitch that is definitely quality. NOW I'm considering breeding but still have a lot to make sure of in my mind before I make that final decision. And it's not all about my dog - it's about how I would feel if anything happened to her (which is always a possibility when you breed), as well as the responsibility of finding long-term, safe and loving homes for the puppies.
There's a part of me that says "yes, yes, YES, I want puppies!!!" and then the other part of me that is logical and realizes that the first part is working completely off of an emotional level .. *L* IF/when I breed my girl, I want to be able to face the dog world KNOWING I did the right thing, instead of having people muttering behind my back about poor breeding techniques.
Melanie and the gang in Alaska