Pit avocados. Scoop flesh into a food processor, add sugar and lemon juice, and whirl until smooth. Add sweetened condensed milk and coconut milk and whirl to blend.
Pour mixture into an ice cream maker and freeze according to manufacturer's instructions. Freeze a metal bowl.
Scrape ice cream into cold bowl. Cover and freeze until firm enough to scoop, about 2 hours.
*For a delicate flavor, buy real coconut milk. For a bigger coconut hit, buy a product made with coconut extract.
Make ahead: Freeze airtight up to 2 weeks.
Note: Nutritional analysis is per 1/2-cup serving.