Can you ride bikes on the trails

Probably, but there are a lot of people hiking usually. Would slow you up a bit

I don't believe the trails can be Ride on a bikes, I saw sings with no bike's allowed , and for the water fall trails is a big no I don't think are safe for bikes I visited this place multiple times and never see a person raiding a bike on it.

The paved trails in the campground area do have signs painted on them that say "foot traffic only" I am pretty sure the trails outside of the campground area do not permit bicycle traffic. The rangers were not enforcingthe foot traffic rule within the camp ground while we were there. I would expect a warning in the campground before a ticket. I would not be surprised to get a ticket on the Riverside trails if riding a bicycle.

There are specific trails for bikes

Far as I know. But I've found pleasure in walking, "two miles per hour, two miles per hour."-From Two Miles Per Hour

I dont think they are wide enough actually given the traffic..

yes