1. obviously program dependent, but I think its way to early to send out emails to PD, would wait until end of August
2. I actually thing its pretty effective, would only do for a few programs, I think the number one reason would to be explain your ties to the area, or any specific reason why you like the program (IE they are a motility center, and thats your research). I think ERAS doesn't always convey geographical ties well and sending an email helps cement any local ties (helped for me); also asking mentors to reach out is important