Gov. John N. Dalton, acting favorably on three measures affecting Northern Virginia, yesterday, signed a bill that would permit Reston to become a town with its own mayor and council.

Other bills approved by the General Assembly and signed yesterday and Monday by Dalton relax the tough state limitations on mixed-beverage sales in restaurants and require annual automobile emission inspections in the state's Washington suburbs as well as in Richmond.

Though Reston could acquire a number of powers under the bill signed by Dalton, there are strong indications that a majority of the 35,000 residents of the planned community are happy being just another part of Fairfax County. Many residents said they fear town status would mean more taxes and a duplication of services.

Voters in Reston will decide the question in a November referendum.

Under another bill signed by the governor, restaurants serving mixed beverages will no longer have to limit their alcohol sales to the same level as food sales.The new limit for alcohol sales will be 55 percent and 45 percent for food. Restaurants also will be able to count sandwiches as meals. pThe legislation was sponsored by Sen. Richard Saslaw (D-Fairfax).

Northern Virginia restaurants pressed for a loosening of the strict rules after several establishments' licenses were suspended when their alcohol sales went above 50 percent.

The General Assembly at first balked at passing the automobile emission inspections bill, but relented when the U.S. Environmental Protection Agency threatened to cutt off $100 million in federal funds that go to Virginia.