In a small bowl, whisk the oil, vinegar, salt, and pepper together.
Set aside.
Serve the salad on a platter, arrange the tomatoes, avocados, jicama, radishes, and jalapeños in rows.
For a mixed salad, put all of the ingredients in a bowl.
Drizzle the dressing over the salad on the platter, or toss with the vegetables for the mixed salad.