Murzyn Hall in Columbia Heights, my cousin's reception was there and it was fun. Other halls are a good option, hotels and restaurants won't let you bring in outside vendors, nor do most big name spaces like the botanical gardens, etc.
You could try the MN Boat Club in St. Paul. I think it would be a great location for a July wedding. However, it depends on how many people you will have as we figured it would only comfortably seat 130 people.
As 'Jaive' stated, it probably will be difficult to find a place that will let you completely cater the evening yourselves. But, you may be able to get the dessert buffet (or something similar). We were able to convince our reception location to let us do a "candy bar" - we just said that it was the wedding favor for our guests.
Be creative! Enjoy the planning and your big day!!!
The Cinema Ballroom in St Paul is Beautiful and allows you to bring in your own caterer. It's a must visit, the pictures online doesn't do it justice. If you're looking in Mpls then try the Ukrainian Event Center. They hold up to 400 guests and is very reasonably priced as well.
The Semple Mansion/Grand Palladian Ballroom allows you to bring in your own catering & liquor, but the rental fee just for the mansion is over $5,000. Many other places we looked at were around that price with food included! BEAUTIFUL building, though.
Many community centers will allow you to bring in outside/your own food, and are reasonably priced. If you are looking for super-cheap options, find a VFW or Elks club.