IMHO, I would look favorably upon a candidate who takes the initiative on their own. I would recommend contacting the BGO instead of waiting for him/her to contact you. I wouldn't hesitate to contact your BGO, there is no reason why you can't introduce yourself now -- though, remember some do go on vacation.
I would favor email over the phone, though either way is acceptable. I like email better because most BGOs work other jobs and might not be able to answer the phone when you call, it gives the BGO a chance to respond back when convenient for them, and it might allow the candidate to explain a little about themselves that can't be left in a short, concise voice mail. Though, if you do email and don't get a response within a week or so, I would then follow up with a phone call.
You can always ask in the first call/email which communication medium is better for that BGO.