"I want to get back together but not right now."
Puhleeeese!
TRANSLATION: "I think I have a new man, but until I'm sure about him I want you to wait patiently by the phone in the event I call."
Dude, don't fall for this. It's an old trick. Put this girl in the files and move on. If she was REALLY interested in you, and if she REALLY wanted to get back together she would find a way.
Regarding this new girl: go for broke, BUT.. remember that women like a man who is CHALLENGING, and is MYSTERIOUS. Don't reveal too much about yourself to her for a while. Make her curious, and most of all go slow. Most guys blow it by moving too fast too soon (i.e. talking marriage on the 3d date).
If you are patient and play it cool, she will be chasing you, which is what you want.
BTW - if you meet another girl who you find interesting, ask her out too. Dating/relationships is a numbers game, the more you play, the better your chances of finding what you're looking for.
Good luck and let us know how things turn out.