Thank you for your reply.
Actually, we wanted to travel early in the year so it could be more affordable than in the summer. We are planning on doing national parks, maybe not a lot, we still want to be visiting the big cities since my boyfriend and I only went to NYC.
Thank you for your advice about camping, we are planning to do some camping in the parks and stay in hotels/motels/airbnb/couchsurfing in big cities.
About work, we ask for a sabbatical, so it's not a paid vacation. But we do have 5 paid weeks vacation per year in France which is really cool indeed.