I stayed at the Green Hotel for a weekend in 2015 with my Vietnamese friend. We had a seaview room, everything was good and nobody cared that we were sharing a room. We went to the Blue Moon gay nightclub which was quite a good and friendly place but the music was ear splittingly loud even for my 21yo friend. Take some ear plugs if you go there. I have not tried any other hotels at Vung Tau but I doubt if you would have any problems checking in with a local guy at most of them.
http://www.agoda.com/green-hotel-vun...ng-tau-vn.html