G,
The timing does present challenges. As you approach your A race, your training should start to mirror the race environment as much as possible. A lack of altitude and lack of incline will have an impact on your training.
Yes, stick with the plan and run the hills as much as possible, even if you need to run up and down the same hill over and over.
Be prepared that your pace for a given perceived effort at altitude will decline after being at sea level for a month. There is not much you can do about that now. It won’t ruin your race, plenty of successful ultra athletes live at sea level.
David