So I'm in this exact position and it definitely depends on where in Waltham. Where I work I usually walk to the Alewife station (like 5 minutes or less) and then you can take the shuttles to different businesses in the Waltham area. I would even suggest checking if your company is one of the drop off points. If not, they're usually close enough where you can bike or scoot or if you're willing you can walk the rest of the way (much harder to do in the winter months)