The sellers bank is under no obligation to accept a short sale although in most cases it is in their best interest. Some banks will respond in a week or so. Others may take several months to decide if they will accept or reject the short sale. Often a seller will accept several offers and their bank will choose which offer to accept. Short sales are not for the weak hearted. It is true that you can get a good deal but you have to ask yourself if the wait is worth it.
You can always continue to look at houses. Nothing is stopping you from doing this but, DO NOT write an offer on any other properties until you are fully released from your existing transaction. Doing so may put you in a situation where you will be bound by 2 contracts. This could get ugly!
Good luck in your transaction. I hope it all comes together for you!
Do you have a Realtor assisting you through this short sale purchase? I would confer with him/her and get an idea of what length of time they anticipate the Seller's Lender is expecting the process to take. I would assume you may have put a clause in your offer giving a deadline by which the Seller's lender would have to give you an answer, or you could call the deal null and void. Short Sales can take anywhere from 4-6 weeks to several months- there is no set answer.
There is no reason you can't look at other homes if you wish.
All the Best to you!