Give the taxi driver following directions and phonenumbers:
Frente entrada principal de residencial "LA GIRALDA".
10 minutos del aeropuerto
PLEASE NOTE: It should only take 10 minutes at the most from the airport, and will cost $4-6 (USD). It exists another B&B which is also called Margarita but is located in Largarita, around 30 minutes from the airport. Make sure you emphasize LA GIRALDA to the taxi driver.
If you are arriving by BUS:
Take the bus from the Parque Juan Santa Maria (approx. 200 colones) in the center of Alajuela, with the sign in the window that says "Giralda". The bus ride will last approximately 15 minutes (depending on traffic), and you will pass by a big, gray hospital, (San Rafael), Invu las canas (there are a lot of taxis), and then you will enter a suburban living area. You will get off at a small, striped guard house to your right hand side at Giralda.