We sent out passport save the dates one year in advance. I wanted to give people plenty of time to save money and book their flights, etc. To be honest, people are still waiting til the last minute and prices have gone up quite a bit, so I can't say that it really mattered but at least no one can say that I didn't try.
Our invites will be sent 3 months in advance with an RSVP 2 months in advance. We are sending invites to everyone, but that's only because we partially DIYed to save some money. I see no problem with only sending invites to guests that you know are coming - the main purpose of the invite for us anyway was for them to pick their meal choice anyway.
Keep in mind that the message in a bottle invites can be expensive to ship if you are trying to save money. The cheapest route, postage wise, is a standard invitation - not a square one which costs extra. For us - we included lots of info on the save the date, then on the invite the only trip info we included was a card with travel and accommodations which had our contact info for questions and our wedding website. We figured that by the time invites came out people would mostly be booked anyway. Then, we'll send out a brochure with airport details, what to pack, etc that will go out a month before to those that booked.
Another thing we did was supplement the save the date and invite with free postcards from vistaprint. We sent a standard postcard letting people know fights were posted online and giving them our group discount code, and we sent a large postcard with some activities in Cabo to give people an idea of what they could do and get them excited about the trip.