I hope I don't screw things up here by offering a slightly counter opinion...
A huge lesson of The Movie (as I speak of it among friends) is to not let fears and inertia steal chances to be happy. The easiest change to make is no change at all, but often that leaves us with regret down the road.
however...
Don't forget to be careful and realistic about this, too. Think about what you REALLY feel about your current guy. And think about what your REAL chance with the jock-from-the-past is. And then decide.
In cases like this there's always a danger that the jock-from-the-past looks better than it is:
--Is he in fact available, interested in the type of relationship you really want (for example, a long-term one if that's your goal) and good material for such?
--How much of your excitement about the jock is simply a rush of the old feelings of an idealized old time...when you were younger, went out more, didn't have a care in the world, and had steamy forbidden fun with a hot straight-like jock? Hell, that sounds great to me right now! But that kind of heat doesn't last under the best of circumstances. Not to say that you're having a mid-life-crisis, but this is just the kind of thing that stokes them, and sometimes makes people make poor choices.
--Are your feelings for your current prison-man more fraternal than anything? Long-term love generally migrates into more of an attachment love than a lustly romantic love, and that's normal. That kind of love tends to be deeper, and can have just as much longing and attachment as the hottest lust. But that doesn't mean you eventually love him like a brother. Some relationships get by on that kind of fraternal love just fine, but frankly it can be better than that.
Lastly, even be a little practical. Is your prison guy away for sixty more more days or sixty more years? Assuming you didn't meet the guy while he was in prison (!!) how WAS your relationship before he went away? Really? Was it not so good, and him going away was in some ways the best thing that could have happened, ultimately? Or does it only pale because you're weary of missing him, and now all the feelings of the good old days have rushed back in a rose-colored-glasses sort of way because you heard from the jock?
I certainly don't know the specifics of this, so I can't tell you which side of the coin you're on. If this is a real chance of deeper happiness, make an active choice and don't let inaction decide for you! But on the other hand, be realistic with yourself. Running off into the sunset with the jock isn't going to turn life into eternal spring break again. You won't be 20. You'll still have that same crummy job, or that credit card debit, or that sister than pisses you off, or that receding hairline, or whatever other things make life less than ideal. The jock won't fix that stuff. Picture yourself 3 years from now, assuming you're interested in a long-term relationship. Will you be better off, happier with the jock? Maybe you don't have a good guess on that answer right now. But you owe it to yourself to try and figure it out. And then based on that, make your decision.