For local customers only, yes you can! You can update your meal plan to be a mix of vegan/meat protein by clicking on "Meal Plan" (linked) in the drop down menu under your name that's in the top right corner.
From there, click "Edit" to the right side of "Meal Plan".
From there, you'll see the words Quick Picks and Custom. To do a mixture of vegan/meat, select Custom. Then click edit to the right-hand side of the delivery cycle you want to modify (Early Week or End of Week, like opting into one or both of those); you can create a combination of meat and vegan on the following page.
On the Edit page - scroll down to find the meat options:
Make sure to click 'Save Changes' and changes to your meal plan need to be made by 11:59pm PST Thursday prior to the week you want the plan updated.
After creating a custom meal plan, to view what you'd be charged for the upcoming week, you can head to Upcoming > Charges. To see what the upcoming items would be in your deliveries, head to Upcoming > Deliveries and you can swap items there if there are items you don't prefer!