I've been to Ben Thanh a handful of times in the past couple of years. Although it is not in the best area, as far as being out on central ave, you can't really find good authentic vietnamese until you get out to areas like this.
The restaurant itself is nice and pretty clean. The food is what is best. Their vietnamese spring rolls are pretty standard, still good.The papaya salad was another great appetizer. Their Pho is VERY delicious. it's not the typical Pho that will put you to sleep after you eat a huge bowl full, and they also load it up with meat. What also is really good is their vietnamese crepe (banx xeo) tastes just like how my ex gf's mom made them. Very crispy and delicious with fish sauce.
All in all, highly recommended. If you like vietnamese food, I would definitely say try this place out.