I also mountain bike, but have had several close calls with cars on the way to the trail. I now limit my biking to weekends.
Yet, as far as indoor machines go, the Concept2 is better than a stationary bike. It is more whole body and is truly grueling. And it's addictive after you develop a routine.
Concept 2 has a website where you can download you daily row and compare your performance to rowers around the world. And there are tons of videos on performance and rowing form.
I would just drive my bike to the trail. Especially here in Florida.
I was coming back from hiking with my dog last Sunday, and I saw a cyclist riding in the right lane on one of our many narrow two lane roads of certain death. I know she was on her way to the paved bike trail, but I would not even walk on the side of one of these types of roads.
Truly dangerous, Florida left no room for anything other than cars on these roads.
I do my inline skating on a closed circuit track. No cars allowed. So I feel nice and safe there unless I fall and bust my butt.
The only exercises I am willing to do indoors is my weightlifting and ab wheel and push ups. I confess that i do these while watching tv.
but as far as rowing goes, I really have been wanting to get a kayak, not the sit in kind, but a larger one that can also hold my shepherd and backpack, and go kayaking and camping with her.
I just love being outside. There is really nothing better.