Can you refinance a Sallie Mae signature loan?

There is no prepayment penalty or exclusion clause in Sallie Mae lending. You may pay any amount above the minimum you want. Therefore, you may pay the loan off at any time. Hence, anytime you have the funds, either by borrowing from someone else (or getting a new loan by them) or from other endeavors, you may pay it off. If you can qualify for another loan, with or without the requirement you payoff the existing one, is entirely between you and the new lender - and dependent on all the normal income, credit rating and other factors.