I can only tell you the situation in Long Beach since I don't know the others!
There will be 1 native English teacher & 1 PTH teacher for each class + 1 chinese assistant! They told me that they would have 2-3 days for English and 2-3 days for PTH each week. All classess are conducted in either English or PTH. They won't mix it in one day!
There is homework each day but it's quite simple like colouring, alphabet, mathematics, songs etc. and then all homeworks would be distributed to parents on Fri for revision and returned to school on coming Mon.
So far, I am quite satisfied with the academic level and my kid likes alphabet & numbers very much!