I would expect to receive a lot of support from upper management at Facebook. As soon as I got there, I was introduced to so many different individuals throughout my team and met many people throughout the higher-up structure of my team. As a data scientist, you work with many different team members, so you'll be able to meet product management leadership, engineering leadership, business leadership, etc.
Expect little support from upper management. While you can reach out as an intern, usually you interact primarily with your manager. Your manager is the one who decides whether you get a return offer or not, even if you primarily work with other people.
Every week I have an hour one-on-one session with my mentor to discuss the progress of my project, my performance. Every other week I have an hour one-on-one with my team manager to discuss my feeling of working with the team. I can always ask questions in these sessions. And my mentor told me to ask him questions whenever I have a blocker on my task.
Your main point of contact throughout the internship is your intern manager. I don't recall interacting with any high level person outside of the Q&As. That said, even though I didn't interact with upper level management directly, they were all very supportive of interns in general and did their best to make it a good experience.
After the three week training, you and your team will be placed into an fb team with a manager. Your manager will have weekly 1:1s with you to talk about your progress and your project. Personally I found it more helpful to ask my team members if I had something to debug just because they were right next to me and more familiar with the codebase of our project. But in terms of career development and how on track you are for a returning offer, your manager will certainly give you support for that.