You can go, but there is no guarentee you will be seen. After all the equity members have been seen, the director has the option whether he/she wants to see the non-eqs or not. So you could wait all day and not be seen. Usually you will not be seen, there is about a 15% chance of actually getting in.
I'm non-eq and I have been seen for every show I auditioned for except for Wicked, including Sister Act, In The Heights, Legally Blonde, Kinky Boots, Bare...I'd say you have a good chance of getting seen IF you get there early enough. Sometimes they'll take the first 15/20 non-eq so they won't see everyone but I wouldn't say "15%" Break a leg!
Also don't expect to be in front of anyone important. By the time non-eqs get scene, it's very rare that anyone important from the creative team will be around. Usually you'll get an assistant director, sometimes not even that, maybe the assistant music director.
No. BUT I have had several callbacks for big shows. So there is hope! Lol. But, it's really a hit or miss unfortunately. It all depends on whether the casting director feels like sitting around any longer than he/she has to.