Are dogs required to be on leash at all times, or just in swimming areas and on trails?

Yes

At all times especially on trails because of mountain bike Riders

All times

All the time but I have had my dog in the water without a leash and they didn't say anything to me about it.

All the time. But I don't know how much they inforce it.

Yes at all times or ranger will give you a ticket 🎟

At all times they are aloud on a leash! But they are great to take.