I visited Guatemala during my nine weeks travel through Central America. After Guatemala I went to Belize and got back to Guatemala to travel onward to Honduras and El Salvador. I made a round trip, in order to travel less and see the most! See here a route suggestion including and excluding other countries.
I found it very easy to travel in Guatemala; tour operators everywhere and transport via shuttle and direct to the next destination in Guatemala or even Belize, El Salvador and Mexico. So no chicken busses needed here, direct with other tourists in a shuttle bus. The distances in Guatemala are not far in kilometers, but the roads are not the best. Some roads are not even paved, winding through the mountains and busy with trucks; it will take time and you have to be patient. Just enjoy the scenery passing by or catch up some sleep!
Compared to Mexico you can’t travel by night in Guatemala. I understood there is only one night bus between Antigua and Flores, but I did not take that bus. I ran into people that took a flight from Guatemala City to Floes. I suggest to take the time and make overnight stops in between the highlights.
I skipped this busy city, I heard it is not really safe and interesting. Suggest to go directly to Antigua upon arrival; the trip is ±1 hour depending on traffic.
First 3 days to overcome a jetlag and feel the vibe, take some Spanish lessons to get comfortable for your coming trip. Split the time in Antigua in two and in between you go to Lago Atitlan.
Spend 4 days around the lake to chill a bit, sightseeing the volcanos and do some yoga to relax a bit more. Enjoy the sunrise and sunsets with erupting volcanoes in the back.
2-3 days back in Antigua and ready to climb the Acatenango Volcano and do some more sightseeing in this amazing town.
Sleep 2 days/3 nights in Lanquín, this is enough to visit the beautiful Semuc Champey nature wonders and enjoy the scenery.
From Lanquín/Semuc Champey you can go first to Rio Dulce for 4 nights and combine that with a daytrip to Livingstone; the Caribbean beach town of Guatemala. If you decide not to go to these places go directly to Flores after Lanquín.
Next: Head back to the south of Guatemala, Mexico or continue to Belize. If you want to have beach time in Guatemala you can visit El Paredon at the Pacific Ocean. Antigua is a perfect base to travel to Mexico, Honduras and El Salvador.
Tip: I noticed that a lot of travelers rush literally through a country. That is not my style, I prefer to see and explore and get in touch with the locals and surroundings. It is still a holiday a bit of relax time now and then is necessary; you don’t want to need a holiday after your traveling!!!