To my knowledge, self driving in those countries is the best option. In Costa Rica, Nicaragua, and Panama traveling by public transportation could be sometimes a fair option, but in Guatemala and Honduras must be avoided at all cost. The insecurity up there is a real deal, , but the most of the violence is not directly targeted to tourists, as far as you keep on the tourist track. On the other hand, the quality of the roads, the infrastructure in general and the signage are far better up there. Still, I would have some degree of precaution driving to Tikal.