in the Phoenix/Mesa/Gilbert/Tempe area. Additionally, there are a host of ward buildings, many within a few blocks of one another.
There is no need for infrastructure: simply use the existing chapels which sit empty all day and most evenings. Spend infrastructure money on good teachers and put them in the existing buildings. Problem solved.
As to who leaves Provo, its the other way around. Start them with classes in chapels and then rotate them into BYU for 2 years, making a higher percentage of those attending BYU juniors and seniors.