If you see one it is warning you to take care and be discreet where persons of the opposite sex are concerned. If you are in one it is a dream warning you against carelessness of speech or behaviour.
A dream of an ambulance is an omen that could be taken as a warning against carelessness and indiscretion leading to some major catastrophe in your life. In all cases it is concerning itself with your health, or the inner fear you may have of having contracted some kind of disease, and warrants a trip to the doctor to set your mind at ease.
It is generally a dream of warning against indiscretion in relations with the opposite sex. America: A dream of going to, or being in, or observing America is an omen of good luck and great happiness through family unity.