Anyone been to Marino las Baulas National Park, Guanacaste?

I was wondering if anyone has been to Marino las Baulas National Park, Guanacaste.
Looking for suggestions for the park. I have read there is a mangrove. Are there any suggestions that you have that we can do by ourselves rather than have to spend a lot on a tour?

I know that at certain times of the year we can see the turtles laying their eggs.

Also, is anyone familiar with a website that talks about trails at the national parks?

Thanks so much:)