Most Filipino restaurants are buffet or turo turo style, which works well for the target market of cost conscious Filipinos. However, that leads to mediocre food. That's where Thelma's comes into play. The best Filipino food in Vegas, period.
Thelma's is a casual sit down Filipino restaurant where you order at the counter and food is later brought out to you. It has most of the Filipino standards, as well as a few Hawaiian dishes with a Filipino twist. At my most recent visit, I had the Adobo Loco Moco. The adobo broth had a great balance of soy sauce to vinegar and was delicious. Every other dish I've had here has been on point.
The dining area is clean and it looks like a legitimate establishment. There are some Filipino restaurants that I would hesitate bringing a non-Filipino friend to, but not here. Thelma's isn't groundbreaking with its decor, but it's a place that won't have you worrying about health code violations.
Prices are a tad more than what you'd pay at a buffet or turo turo style Filipino restaurant, but it is still a solid value and is more than made up for by the increased food quality.