You could explore up on the mountains. Drive east on I-8 to Sunrise Highway, go north over Laguna Mountain, then
drive through Cuyamaca State Park and Julian, and come back through Ramona back to I-15. If you do that, make sure to stop at Dudley's Bakery in Santa Ysabel to get a treat (it's between Julian and Ramona).
Another idea this time of year is you can hike parts of the Mormon Battalion Trail out east of the mountains in the desert.
If you want to do a nice walk/hike, I recommend the ~6 mile round trip walk in Los Penasquitos Canyon Preserve from the east end off Black Mountain Road to the waterfall and back. If you do that, say "hi" to my Eagle project for me (I organized a crew to make the stone steps that lead down from the trail to the waterfall).