...and how do you pronounce it?

Quince (pronounced 'Kwinss') is a flowering fruit tree that produces tart, seeded, yellow fruit that looks and tastes similar to an apple and/or a pear. Internationally, it is used in pies and jellies or jams and is rarely eaten raw. Quince is also a flowering bush that is popular in suburban U.S. landscaping. Quince Street in Denver is named for the fruit tree and is the home of Quince Coffee House, hence our name.

...Isn't it the Spanish word for "fifteen"?

Quince (pronounced 'KEEN-say') is the Spanish term for the number "15" and we are delighted to have a name with so many meanings. Please DO feel free to pronounce it either way! (BTW - quince the flowering fruit is called "membrillo" in Spanish).