We went in March. First half of the week in Tamarindo. Great beach, terrific surf, fishing was cancelled due to steady 25-30mph winds. It was "windy season"... who knew!? I was going to fish on a panga boat, not too far out, with "Pedro's fishing" guide or whatever. All I can say is that they guy (Jason, Pedro's American son-in-law, who apparently runs most of the fishing trips) was a real [censored]-head on the phone. Just an attitude. I was almost glad I didn't have to spend a day with the jerk on a boat with my son. So... Sorry I cannot advise on a guide.
Second half of the trip was inland, near Arenal Volcano. Didn't think of it or have a plan, but freshwater fishing can be had. There are some beasties in the rivers. I can get the guide company that we did an eco-rafting trip with, as I recall seeing fishing trips advertised. They were a good outfit. You may want to take a travel rod and maybe some tackle. I wished I had.
Other than that, awesome place. We loved it.
Ride to fish! Fish to Ride!