Check with PRO, they can suggest you the best as they are the one who goes and does the visa thing done.

as much as i know if you have not taken their visa and and u didn't finish the probation period or you have not received the confirmation letter from the company, any moment you can leave the company..

but... also it's important to know what kind of offer letter they prepared for you? first u check this and then take any step... anyways Good Luck........