This is my current favorite pho place in Las Vegas. I go once every week to 10 days, or so.
Pho hung never fails to satisfy my cravings for noodle soup. I always order the same thing: pho tai, with the beef on the side (so I can drop it in to the broth at my leisure, and keep it rare), and an order of spring rolls - shrimp only, hold the pork.
The broth is always perfectly seasoned, with a rich beef flavor - never greasy or watery. Each bowl is generous on the noodles, and comes with the customary plate of bean sprouts, limes, herbs, and chili peppers.
Sometimes, when I've got a big appetite, I order an extra plate of beef slices for $3. Even with this addition, my meal never costs more than $15 total. I always have left overs. Pho makes a wonderful meal on the cheap.
Pho Hung is also good for late night dining. They're open every night until 2am.
Like many eateries of its particular genre, the service can be quite lackadaisical. I'm personally willing to overlook that for the quality of the food and the low price.
The dining room itself isn't what I'd call attractive. it's harshly lit, and a little gaudy - though always very clean.
If you love pho, give this place a try.