It also depends on what size plane you are flying in. In a larger plane you will feel less of the "bumps".
Flying into and out of Los Angeles we did not have any turbulence, Salt Lake City, that is a different story, flying in and out we experienced significant tubulence. I fly fairly often, and had never experienced that kind of motion on a plane, I was concerned. But once we got to a cruising altitude it was fine, I think it is just rough because the city is surrounded by mountains.
Don't worry you will be fine, just keep telling yourself that a plane is safer than a car. Also, if you have a phobia, medication may be a good bet. Don't be afraid to ask your doctor for a perscription, take a test run of the medication first, to make sure you don't react adversly. Good Luck and happy flying.