Getting to Kaieteur Falls overland is one of the best adventures in Guyana. One can fly in from Georgetown but doing the 3 day trip by bus, boat, and hike is an experience you won't forget. Being a rainforest, it is not unusual to get drenched during the trip or having to walk through knee deep waters. We were lucky to have great dry weather throughout the trip through some would say that the rain is part of the rainforest experience!
"Kaieteur Falls is a waterfall on the Potaro River in central Guyana. It is located in the Kaieteur National Park. It is 226 meters (741 feet) when measured from its plunge over a sandstone cliff to the first break. It then flows over a series of steep cascades that, when included in the measurements, bring the total height to 251 meters (822 feet)". source: http://www.guyanesepride.com/about/kaieteur_falls.asp
Our group went with Tony who is a local guide very familiar with the region and he is a great story teller and cook. With Tony you should be willing to rough it out a bit though. He can be reached at +592-686-6547 or +592-680-9089. You may need to leave and message and he will get back to you.
If you want a "bit" more luxury, there are other tour companies which also offer the overland trip such as the Rainforest Tours and the Wilderness Explorers. You can also fly in and out with a brief 2 hour stay at the falls with a couple of local airlines flying out of Ogle airport in the city.