We’ve been really happy for the last 2 years in San Elijo Hills, a master-planned community in the southwest corner of San Marcos. Great schools (very high APIs), special neighborhood feel with walkable town center (Albertson’s, Hendo’s, Yogurt Utopia, dry cleaners, Relm Wine Bar, Cafe Stoked, etc), tons of hiking trails and pretty close access to Carlsbad and Encinitas retail/beaches. All in all, it’s been a really great community where neighbors, at least in our subdivision, really look out for eachother and their kids.
Definitely not as ‘prestigous’ as the Crosby or Santaluz, but your commute would be much shorter to Fallbrook and the community offers a lot of what you’re looking for without outrageous HOA/Mello Roos.
Davidson Communities purchased 10 homes on the most premium lots in the master plan a few months ago and plan to release them right in your price range, I believe. Panoramic ocean views and pretty big lots.