Don't reduce serving pressure. Reducing serving pressure means your beer will go flat! Serving pressure should always equal carbonation pressure, or else your carbonation will drop until it does.
Your bubbles are CO2 coming out of suspension. This is caused by one of many situations:
Your line is too warm. Do you have a fan or something circulating air in your kegerator? If you have a warm spot in the line, as the beer passes it CO2 will jump out of suspension.
Your beer is overcarbonated for the pressure you are dispensing at. If your beer carbonation pressure is higher than the pressure you are serving at, CO2 will come out of suspension. How did you carb your beer? Is your regulator set at the correct carbonation pressure?
Your reg pressure is set below your carbonation pressure. Similar to #2 above, but with the fine distinction that you didn't overcarb your beer, but are holding it at a lower pressure than you should. As the beer sits in the line, at a lower pressure then, CO2 comes out, and shows up as bubbles.
These are the things that cause bubbles in the line. If you are getting super foamy beer when you dispense, but no bubbles in the line, it's because your lines are too short, (system not balanced). If you increase reg pressure to the correct carbonation pressure and get foamy beer or too fast of a pour, then increase line length.