This is indeed an old thread, but still very relevant. Frankly, I don't know what I would do without Taca/Lacsa - I've flown them from Los Angeles for every trip other than my very first to CR (14 trips now), where I used miles on United and had to connect in Washington D.C. - never again...
First of all, as Nuckinfuts already stated, the itinerary is perfect. Redeye out of L.A., so no hassles getting to the airport, you sleep on the plane, and arrive around 8am with no customs line whatsoever at SJO. Then, late afternoon departure out of CR, so you get the whole extra day on the tail end, and arrive back in LA before midnight (again, no customs line and no traffic hassles - always a big factor here). I usually get direct flights, but even when required to connect in El Salvador or Guatemala it's never been a hassle, and only adds slightly to your overall trip time.
Moreoever, having flown them so many times, I've been able to use miles for free trips twice now as part of their Distancia FF program. This also gets me free first class upgrades most of the time, which makes a HUGE difference on a long flight. Planes are newer on average, food is better than average, alcohol in flight is FREE, and having a cute Latina flight attendant serve you with a smile and a sweet "con mucho gusto" is the icing on the cake.
I almost hesitate to post this, as the secret seems to be out and rates keep going up all the time, but nevertheless, for me this is the only way to go.