Should I sign a abritration with my new employer?

1) If you sign the agreement, you are bound to its terms. Without seeing the agreement, we cannot advise as to what those are in your specific case; that said, as a general matter, when you sign an arbitration agreement, you give up the right to sue, such as for alleged wrongful termination or breach of contract (if you have one). Instead, the matter would go and be decided by binding (enforceable) arbitration. Again, that's the general rule: you need to review *this* agreement to see what it says.
2) If the agreement is to arbitrate disputes instead of suing, then based on my experience with arbitration, I would tend to recommend against signing if given a choice.  Arbitrators are often pro-employer: they are frequently attorneys who (when they are nt arbitrating) represent employers, not employees, or retired business people. Also, arbitration decisions are generally not appealable or reviewable--certainly not as easily appealed or reviewed as a court decision; if a bad decision is made, you are stuck with it. And while the theory is that they are less expensive than court cases, assuming you hire a lawyer to represent you (which you should, since the employer will have an attorney), they often cost about as much as  trial would, so you are not saving much in exchange for accepting the other disadvanatages. The fact that your employer wants you to sign should tell you that they feel arbitration would be to their advantage.