We would recommend starting with either La persona especial
or SOMOS 2 Unit 1
. Both of these units are very student-centered and fairly “free”, which allows you to really see what language your students have previously acquired. Once you have assessed where your students are at based on their ability to communicate in those activities, you can backtrack to SOMOS 1 units–possibly Unit 1 or possibly to a later unit. Students will enjoy the units from Level 1 even if the language is a bit basic for them because it is a completely different way of teaching, and their brains will be working and engaging in a different way.
We would also recommend asking the class stories from Level 1 in present tense, but reading them in past tense, as past tense is an important component of most Level 2 courses, and your Level 3+ teachers will expect students to have had significant exposure to it when they enter their courses. Some teachers do this present/past pairing even in their level 1 courses.