No federal OSHA rule says an evacuation map has to be printed in Spanish. What OSHA does insist on is that training is understood. Its 2010 policy statement on training covers general industry, construction, maritime and agriculture, and it is quoted on the right.
The same memo says that employers who usually give work instructions in Spanish (the foreman explains the job in Spanish, the morning tailgate talk happens in Spanish) should expect to give safety and health training the same way. Inspectors are told to look at how instructions are really given on your site, not only at the paperwork.
Your emergency action plan has to describe how people evacuate and which exit routes they use (29 CFR 1910.38(c)(2)), and 1910.38(f) has you go over the plan with each employee at three points: when they start or the plan is first written, when their part in it changes, and when the plan changes. Construction companies find the same review points in 29 CFR 1926.35(e)(2). The map is what you point at during that conversation, and it works better when its words are in the language the crew works in.
Companies with 10 or fewer employees may give the plan to the crew verbally rather than writing it down (29 CFR 1910.38(b); in construction, 1926.35(e)(3)). For those crews the posted map is often the only written piece they ever see, so print it in the words they use.