I don't think 'Beer Hoi' is San Miguel, Beer Hoi's are very popular in the North around Hanoi, its generally brewed very quickly and is very weak ~3%ABV, its more of a refreshment than a proper beer, in Hanoi we was paying around 20C a pot for it, in Hoi An it was around 9C, didn't see any in Saigon.
In bottles you get the 333, Hanoi, Saigon, all similar around ~5%. There's an Aussie bar near the Saigon skydeck where we went to watch some sport in, they have more options but you'll pay a lot more in there too and some nice rooftop bars around there also but again they'll sting you compared to a street bar.
Enjoy it, we loved it, sample as much of the street food as possible, we went with 2 kids and the only time either of them got sick was when we ate in restaurants!!!