From Autoblog, Trump is confused about where in Mexico Toyota produces cars and trucks. He needs a briefing from knowledgeable sources before he tweets.

http://www.autoblog.com/2017/01/05/trump-tweet-toyota-factory-mexico/

So let's dispel the confusion here. The plant in Baja already exists, and builds Tacoma mid-size pickups. Toyota has already announced plans to invest $150 million in the Baja plant to expand Tacoma production, but the plant doesn't (and won't) have anything to do with Corolla production under the current plan.

As far as the Corolla plant, it is supposed to be constructed in Guanajuato. Toyota announced these plans back in 2015, and expects the plant to produce around 200,000 cars a year to be sold in North America.