My Experience
I would say, "do not miss it!"
It is normally not too crowded. I went during Semana Santa/Holy Week - mixed with spring break - so there were plenty of DOMINICAN tourists. Not the same (bad) thing as hordes and hordes of foreign ones.
It is not for the faint-hearted among you. First, the path is narrow and steep and muddy. And your guide is a young local boy. And you have folks ahead and behind ya, and no helmets!
But we survived it, and we loved it.
You can get organized via Victoria Marine in Samana, or you can rough it on your own as we did.
We took a gua-gua from the market "station" JAJAJA in Samana toward El Limon. When we neared ANTONIA'S, we let tour driver know to stop. (Her horses are on the left-hand side, but her restaurant is on the right-hand side.)
You talk to her and get a reservation for her yummy lunch or whatever meal it is. And then off you go on your horse. Food is ready when you get back.
She will sell you local cocoa and coffe if you wish. No fancy package, real basic. You can grind the cocoa right into your cafecito.
Enjoy! -- And give us your trip report! -- Sam
P.D. I got all excited about El Limon, and as usual forgot to answer the OP's questions.....
"Any thoughts and recommendations for a guide, etc? Do you think it would be possible to go to Las Galeras after hiking in to the waterfall (taxi,gua-gua, etc.)? "
Antonia will get you one of her guides.
Hiking into the waterfall? Whew. Good luck. Up and down a lot of hilly countryside in the heat!
Yes, you can hike there and back and wait for the next gua-gua headed to Las Galeras. (On the horse barn side of the road - not on the restaurant side).
The gua-gua will drop you in Samana, at the market, and there you can pick up another gua-gua to Las Galeras.