I've made the trip lots of times and spend 2-4 weeks each summer in San Pedro, sometimes alone, once with my husband, and frequently with a group including teens in tow - feels safe to me.

Re: the route between Antigua and San Pedro, I hugely prefer to go by road from Antigua to Panajachel and take a boat across to San Pedro. It's possible to go clear to SP by road but it's longer and the road down to SP from the Pan American is steep and curvy and creeps me out.

Here are 2 transportation providers I’ve been pleased with in Guatemala for share shuttles, private transfers, and flight arrangements:
Adrenalina Tours: www.adrenalinatours.com
Rainbow Travel: www.rainbowtravelcenter.com

Happy trails!

bookmarking

Fun to see this old thing crop up. :-)

My photos with blog, travelogue, and review links on the main page of each collection are below in case you're interested - I've made half a dozen trips to Guatemala since the one documented above. Happy trails!
http://www.flickr.com/photos/staceyholeman/collections

Going to Guatemala for the first time in March, I look forward to reading your trip reports in advance! (although we'll be with a group associated with a charitable organization, so the actual travel, other than our visit to Tikal before the group tour, and Chichicastenango after, was planned by others).

Have a great trip! We're heading back in 6 weeks. :-)