lot's of different things available here:
Carlsbad City Rec pool, $3 per visit, or $4.50 to attend Masters swimming (always a handful of pros at Masters, Jurgen Zack et al). Outdoors year round, temp kept at a great workout level
I also go sometimes to Bally's Fitness ($29 a month) for indoor swimming pool, 5 lanes, I rarely ever see anyone else there.
Club open water swims in the ocean, 4 times a week available, free
Mike Plumb, TriPower MultiSports
Professional Running, Cycling and Multisport Coaching, F.I.S.T. Certified
http://www.tripower.org