Bicyclist -- Writing With (AP) Style

Is it 72nd St. and Southland Blvd.? Or 72nd Street and Southland Boulevard? Or Seventy-Second Street?

In this case, it was 72nd Street and Southland Boulevard. From AP Style, under "addresses":

Use the abbreviations Ave., Blvd. and St. only with a numbered address: 1600 Pennsylvania Ave. Spell them out and capitalize when part of a formal street name without a number: Pennsylvania Avenue. Lowercase and spell out when used alone or with more than one street name: Massachusetts and Pennsylvania avenues.

Spell out and capitalize First through Ninth when used as street names; use figures with two letters for 10th and above: 7 Fifth Ave., 100 21st St.