Milpitas is all about diversity and there are plenty of businesses and grocery stores that serve non-Asian people. There is a Safeway, a Nob Hill and another small market within 5-10 minutes drive.
Big projects like BART usually get done a year or two late but I don't see any major construction challenges.
The area has an exceptionally good transportation infrastructure and I don't think there is any chance of overbuilding. House prices in my part of Milpitas are up 27% in the past year. There is plenty of housing demand in Silicon Valley and Milpitas offers more modern housing at a lower cost per sq ft than other cities.
Supply and demand is always the driving factor on rentals and resale. It is the job of planning to accommodate demand without over building. Keep in mind that most investors are savy and do a lot of homework before deciding to invest and build in a certain area. They have done their studies. If investors are building apartments and planning is allowing it the prediction is that demand will be high.
There is always a possibility of over building. Do keep in mind that Milpitas has a lot of infrastructure in place and is close to services and jobs. If you are worried about a "Mountain Home" community, I would reassure you that should not be a concern.
Just my opinion.