Big protests next will see roadblocks of many main highways and demonstrations in the capital and other cities on August 25-27 (Tuesday through Thursday). Roadblocks begin at 5 AM daily, so the only way to travel to Lake Atitlan and other parts of Guatemala will at night on extremely overcrowded chicken buses, if at all. However, some shuttle companies know the back roads between Antigua and the lake, so check with them.
As of Tuesday, the road from Xela to the Mexican border and San Cristobal de las Casas was blocked. So was the Interamerican Highway in the Momostenango area and other parts of the country.
If flying out, shuttles will likely operate between Antigua and the airport after sundown, so spend the night before your departing flight in the capital to ensure missing the plane.