If you're looking for a more challenging hike, try Haley's favorite (and Brendan's least favorite) 6 mile loop off of Highway 1. Take the Soberanes Canyon Trail in and loop back via Doud Peak. Depending on who you ask, the redwood groves and stunning views of the Pacific are absolutely worth the ~2,000 ft climb. Try to go early before it gets too hot and bring water.
If you'd like to explore Monterey by bike or kayak, you can rent either from any of Adventures by the Sea's 3 locations. The Monterey Bay Coastal Recreation Trail is great by bike or on foot (where Haley learned to ride a bike!), and kayaking tours of Fisherman's Wharf are a great way to enjoy the bay.