Hi, I'm an expat and I live in Salalah. I can confirm that there is nothing you can call a reall "beach scene" here. BUT, the beaches here must be the best I've seen on the arabic peninsula. I've travelled extensively and only the beaches in the Philippines were prettier.
What do we do on the beach here?: Camp, bbq, lounge. With friends.
I don't agree with the above that cafe de paris is the best lounge scene because the sand is full of sigarett butts there. It must be the least clean part of beach in Salalah. The hotels have nice places to lounge. You can go to the Crowne Plaza (I think they do shisah on the beach). The Hilton has the sea breeze bar. And the Oasis club, on a cliff overlooking the sea, recently also opened a smoking area outside.
If you're coming with friends,bring a tent, buy a shishah and a bbq and find yourself a spot on a pristine beach. The most beautiful are just after Mirbat when you come from Salalah. You can drive down from Muscat along the beach and camp along the way or take a plane ride for about an hour. But, hurry up because the temperature is rising. May & June will be hot hot hot. After that it will be "Khareef" and we will not see the sun again until the end of august.
Check out some of the things to do in Salalah on this new site: http://www.secretsalalah.com/ This region is very special and unspoiled. Hope you make it down here!
Have fun!