if you are asked to sign a non-competition clause after you are hired. they have to give you a substantial raise, check, promotion, cash, or something valuable. If not, you are free to go anywhere you want.
A court case in PA just confirmed that. All the details are in this article.
Basically, if they threaten to take away your job and make you sign something saying that you waive the compensation, they have no contract. The actually have to give you some compensation or they lose, no matter what they had you sign.
Make sure you check out the details.
If you want a general review of PA noncompete law, try this article..