I'll be staying in Brentwood (by the 405 and Sunset blvd). Can you please recommend the best Vietnamese restaurant in LA?
Sorry to inform you but you will need to drive over to SGV or Little Saigon. There is no 1 stop shop for great vietnamese food, merely shops that fill to a certain niche: so a descriptor of what you're looking for would be great.
Thus far, I have found Golden Deli in Alhambra to be my go-to 'all around' vietnamese restaurant.
Pho So 1 just up the 405 in Van Nuys, corner of Sepulveda and Victory, is pretty decent. Way better than all other westside Vietnamese. Other than that, you'll have to drive quite a ways farther to SGV or Westminster.
Here's a chow map for you:
You really do have to head to SGV or Little Saigon. Pho So 1 in Van Nuys is decent enough to recommend for those trapped Westsiders (you know the ones: anything east of La Cienega counts as "the east side"), but really, your best bet is to set aside an extra ten minutes of travel time and just go to SGV.