Our favorite spots are the north end of the boardwalk and into the North End or upper streets, which is the more residential part of the beach. Anywhere above 20th street is great! You can park along the feeder road (next to Atlantic Ave).
If you're looking for a bit of hiking check out First Landing State Park! There are tons of trails with lots of different terrain. You can drive up and park for $10 on weekends (or $7 on weekdays), but we recommend parking on 64th street and walking in for free 😉