I have long thought that Costalegre was an agreed upon catch word for the Costa Alegre. Now I'm finding there is another long time standard, Coastecomates. This is about that area as well.
The stretch of coastline located between Costa Majahuas and Cihuatlán is the Costalegre or “happy coast.” Others describe the Costalegre as the area between Puerto Vallarta and Manzanillo. Either way it is still "the happy coast". Pacific Coast of Mexico