Currently there is a consderable amount of construction in Port Huron making it diffcult to get to the hotels in the Water Street area. I would suggest looking at the Quality Inn, which is close to the main North & South route (Pine Grove Ave) through Port Huron and up to Fort Gratiot Twp (shopping, restaurants etc).
The Thomas Edison Inn would be another potential lodging choice with great views of the Blue Water Bridge area and the St. Clair River, however, there is a lot of uncertainty about the Edison Inn as it was recently sold and is supposed to be upgraded to a new hotel/convention center and not sure how long it will remain open.
In any event I think you will need a car to get around. Not sure what your interests are in Port Huron so hard to provide any advice there.
Some good spots to eat would include The Quay Street Brewery (on the Black River) the Vintage Tavern (upstairs has a great view), Fuel, Casey's Pizza (new additon to the facility which was nicely done) Pompeii's for Italian food.
All of those places are located in the general downtown area, but as mentioned there really aren't any downtown hotels worth mentioning.