Add cucumbers to a blender and puree until completely blended. Pour through a fine mesh strainer, or a nut milk bag, into a bowl or measuring cup.
Add the cucumber juice, tequila, triple sec, lime juice and agave to a large pitcher and stir well. Taste test and add any more sweetener or fresh juice as needed.
Run a lime wedge around the rim of the glass, then dip them in salt. To make them spicy (optional), muddle 1-2 jalapeño slices into the bottom with a few sprigs of mint.
Fill each glass with ice then pour the cucumber margaritas on top. Garnish with more jalapeño, mint, cucumber slices or lime wedges.