One of the cheaper options without staying at the hostel, I have not stayed there but was sugested to me by someone that lives in Big Bear. Also not sure about if they have a pool, I doubt it.
http://www.threepineslodge.com/
My favorite rides in Big Bear is Grout Bay/Grays Peak in Fawnskin and Exploration Trail in Arrowbear. Also Champion Lodgepole to Gunsight on Siberia Creek Trail is nice...none of them very long.
Picture Siberia Creek just before Gunsight, trail gets to overgrown to ride in another half mile..