No, in San Miguel de Allende you do not have to purchase your property in a bank trust. In San Miguel, foreigners can purchase their property and hold the title in their name.  

Bank trusts are only required for foreigners who purchase properties within 50 kilometers of the coastline or within 100 kilometers of a land border. Owning a property within a bank trust can greatly increase your closing costs. In addition, the annual fees for maintaining this trust range from $500 - $1,500 USD per year.

Foreigners buying property in San Miguel will enjoy the advantage of not having to purchase within a bank trust in order to buy property here.