Try Lush for a decent selection of WG and local girls just looking for fun. It's a nightclub and they have a FB page you can checkout.
Avoid Apocalype Now and Go2. The WG here are the dirtiest WG Uncle Ho has to offer. You probably catch something bad or very least get scammed, drugged or have all your shit stolen from your hotel room.
Also never go with someone promising girls at an an unknown location. Best case you'll be ripped off, worst case could be a nightmare.
Also avoid the WG/ladyboy on scooters.
Bare in mind prostitution in Vietnam is illegal and being caught engaging or cohabitating with a local in a hotel room can lead to arrest.
Be smart, don't attract attention to yourself and keep your eyes and ears open.
For a bit of fun checkout Rona Massage near Ben Thanh Markets. Also take a walk down Ngo Van Nam street which runs off Ton Duc Thang. You'll be able to work out the deal after not too long
Have fun!