In 1993 I went to Guatemala as day trip from Cancun. I was able to sign up for this tour at the hotel desk. The cost included a plane flight, tour bus pick up at the Gutemalan Airport, tour guide (in English and Spanish), Tikal ruins park tour, Flores city tour, and return ride to the airport and return flight. I had to get a cab to bring me back to the airport. That was the only scary part to do alone.
The second time we visited Guatemala was from Belize, again signed up through our hotel. A lot has changed over the years, and perhaps one can term the area "more stable" now, though the first visit in 1993 was still a safe visit.