Someone who's vulgar has bad taste, and could also be called unrefined or unsophisticated. Your snobby neighbor might mutter about your family's vulgar taste if you paint your house with rainbow stripes.
From the Latin vulgus, meaning "the common people," vulgar is an adjective that can describe anything from the sexually explicit to the merely ugly and crass. Many people believe that there's an important difference between things that are sexually frank and things that are vulgar. "Erotica" can be beautiful and even highbrow, while "pornography" is crude and vulgar. My friend Arnie loves the lights and glamour of Times Square, while Cintra finds all the bright-colored, corporate logos to be vulgar.