I've done the Bogota Rio Claro route before, and I just got off at Doradal and caught a taxi the rest of the way. Some bus companies in Colombia only drop off/pick up at terminals, so make sure you're with a company that is ok with dropping you off on the side of the road. Honestly, if you're on the fence about coordinating to get dropped off on the highway, then just head to Doradal and get a taxi for the rest of the trip. The taxi ride was about 10 min and it cost 15,000 cop. We rode with another local and just split the cost 2 ways. The taxis were lined up on the street that the bus dropped us off on. We just asked some random guy standing around, and he pointed us in the right direction. Also, I'm pretty sure that buses plying the Bog-Medellin route, don't pass by Rio Claro and Doradel. They do pass through La Dorada and you can transfer there to Doradel very easily. Ideally, you'll want to get a bus from Bogota to Doradal. If you can't swing it, then get a bus to La Dorada from Bogota, change there for Doradel and then catch a taxi in Doradel the rest of the way to Rio Claro
We asked the people working at the reception desk in Rio Claro to help us with transport the rest of the way to Medellin. She basically called the office in Doradal, and found out when the next bus was supposed to be passing by Rio Claro. We just headed to the highway around that time and waited for about 5 min. As mentioned before, if you can't get help, then just go to the highway and flag down the next Medellin bound bus that you see pass. The busses bound for Medellin most likely stopped in Doradal, so there's no need to backtrack. You'll see that many rural Colombians catching a bus, just go to the nearest highway and wait for the next bus to come along.
There are accommodations in Rio Caro right next to the highway. If you stay in those, then having a wheeled suitcase isn't a problem. However, the accommodations further in the park, are about 1km from the highway down a dirt road. You probably could find someone at the entrance to give you a ride, but if you can't, you're then stuck lugging that suitcase down a dirt road for about 1km. Skip the car rental and just make reservations in the cabañas by the highway.
Also, you will be taken to the north terminal if you decide to head to Medellin from Rio Claro. Since the buses from Guatape leave from that terminal, then there shouldn't be any transfer issues.
