From the Cedar Park city website:

Fireworks are always illegal within the entire fire service area of the City of Cedar Park, including the City's ETJ (extra territorial jurisdiction), and areas within 5,000 feet (just under a mile) of the City limits. The fine for possessing, using, and disposing of illegal fireworks can be up to $2,000 plus court costs.

The City recommends letting the professionals handle the fireworks.
Don't forget, the first ever Fourth of July Parade will be at 10 a.m., beginning at Cedar Park Center (2100 Avenue of the Stars) and ending at the Cedar Park Recreation Center (1435 Main Street). For more information on the parade and Fourth of July Celebration, click here.