I have a vague idea about the beaches of Dubai.Are there any good ones and do local people enjoy these beaches or they are just visited by foreigners.

I think they are pretty good. At least they were when I was there. They are visited by everyone, not just foreigners. I think in some beaches there are more locals than foreigners. Keep in mind that a lot of the locals are foreign workers so they don't necessarily look like locals. But overall, the Dubai beaches are great in my opinion.