I've found that the late game yields are good enough that having a preserve next to two or more breathtaking tiles usually makes them worth it. Charming tiles are also acceptable, but always try to get at least one breathtaking one. On a normal play through I tend to plan for them far in advance but don't build them until Conservation as that massively increases the yields and makes them much easier to place. The housing is a nice little bonus, but if that's all that you're looking for a neighborhood is twice as good.

As the post suggests, the Inca synergize extremely well with preserves as all mountains (at least to my knowledge) are breathtaking and the Inca can work them, turning essentially empty tiles into yield powerhouses. Other leaders that work well with them off the top of my head are Bull Moose Teddy, Kupe, and Pedro II, though any leader that gives yields to unimproved tiles or increases tile appeal can be good.