I am in San Diego also and it looks like the Peach Leaf Curl that affected 3 of my peach trees... not an expert by any means on Mangoes and not even sure if Peach Leaf Curl could affect Mangoes, but here is info from CRFG just in case...
The fungus survives the hot, dry summer on the trees surfaces.. In spring, the
fungus is moved by splashing water and can infect newly developed leaves.
To prevent peach leaf curl, treat peach and nectarine trees every year after leaves
have fallen. Copper-based fungicides, calcium polysulfides, or synthetic fungicides
can be used.
To be effective, copper-containing compounds must have at least 50% copper.
It is be advisable to apply a second treatment in spring, preferably before buds
begin to swell, but definitely before budbreak (when green color is first visible).
Although symptoms of leaf curl are seen primarily in spring as new leaves develop,
there is little you can do to control the disease at this time. Normally, diseased
leaves fall off within a few weeks and are replaced by new healthy leaves unless it
is rainy.
Development of leaf curl ceases when young tissue is no longer developing or
when weather turns dry and warm (80° to 85°F).