Marbella is a neighborhood in Panama-City (I live there). It is a "live-able" part of town that is favored by expats who do business in Panama. Marbella encompasses most of the banking district with a mix of modern high rises, older mid rise buildings, strip shopping centers, many medical offices, clinics and a mid-size hospital (CMP).
Panama City is on the Pacific side of the country and the average rainfall is about 12 ft per-year. The dry season parallels the dry season in Miami (Nov-April). In recent years, the rainy season has not started untill mid-May and because 40% of Panama's electric power is from hydro-electric dams, the longer than usual dry season resulted in power rationing.
Power rationing does not effect essential services, such as hospitals, hotels, elevators, or water supply. It is a voluntary cutback of power use in public areas, and businesses must shut off the air conditioning from 11 AM to 3 PM.
The biggest issue with the rainy season (anywhere in Panama) are the mosquitos that carry the dreaded Dengue disease.
Hope this response helps you make a decision about living in Panama.