Once Levi and Phenex are settled in with each other, Lucifer flies off to the river. He can't expose himself here with the trees and all the flammable things. However, the ocean front, if truly empty would be a better buffer against the conflagration that was Lucifer when he was exposed.

Balthazar wouldn't be hard to find. Lucifer could already home in on his presence when he was bundled up in Levi. This should be significantly easier.