If you had to choose only one town on Lake Atitlan to visit, San Pedro just might be the best choice. Small enough to be quaint and big enough to offer plenty of activities as well as any supplies and services you might need, it's an irresistible blend of the traditional and the contemporary, with surprises around every corner. Its older part of town consists of a maze of narrow streets that are more like alleys, and you never know what might meet you around the next corner - even a bicyclist, motorcyclist or equestrian you might have to dodge. There are plenty of enticing restaurants, shops and cafes tucked into every nook and cranny. The marketplace is a hive of activity and a fun place to shop for produce, clothing and other items. If you're lucky enough to be in town for New Year's, you'll not only be able to see a dazzling display of fireworks over the lake, but you also definitely should catch a curious little festival in the city center during which the locals dance to a live band while dressed in Halloween style costumes. It's something you may not be able to see anywhere else. San Pedro is also a good launching point for a hike to the peak of a nearby volcano.
If you go:
Unlike most of the other towns on the lake, San Pedro is accessible not only by boat but by road traffic. The best way to get there is to take a bus or shuttle to Panajachel, and from there take one of the frequent water taxis to San Pedro. Lodging is plentiful and inexpensive. If you opt for Airbnb, make certain you pick a host with several reviews, as scams have occurred on the site in this area.
Links:

Third Avenue 2-24
Zone 1
San Pedro la Laguna, Solala 07018 Guatemala
comunicacionmunisp@gmail.com
Phone Numbers:
Municipality of San Pedro
+502 (772) 18095
+502 (772) 18095
Municipal Tourism Office
+502 (406) 99834
+502 (406) 99834