The amount of mercury in a single bulb is tiny. The energy savings of a FL bulb over incandescent lamps is huge. On an environmental impact basis the mercury burden is way tiny compared to the impact of the energy.

As to LED's, they are years off being cost effective. They also do not last anyway near as long as they advertise, especially in a damp environment.

Get a stainless steel fixture, locate sources for cheap replacement ballasts and sockets, and go for fluorescents. CFL just don't have the area coverage.