Where are you based now? How long do you have for the summer? Is money a consideration, i.e. do you need to be paid for your summer time? Could you afford to spend X number of weeks in another city, e.g. in rented accommodation or a hostel?
The first thing to say is that you are planning very early and so I wouldn't rush into any particular opportunity unless it has a fixed deadline. I certainly wouldn't speak to local consultants yet as you will find it difficult to back out if something "better" comes up in the meantime. Local consultants would probably entertain a keen student for a summer without any difficulty or much notice. You will also have plenty of time to hang out with them during your clinical years...
It's probably worth thinking seriously about likely specialty choices at this point. Obviously you won't be committing yourself (and shouldn't commit yourself !!) but might as well do something that's as likely as possible to pay dividends later.
It sounds as if you are interested in the "high octane" specialties which isn't uncommon amongst medical students and might wear off in the future - but it's a place to start. A&E doctors, acute physicians, anaesthetists, intensivists, vascular surgeons, general surgeons, and orthopaedic trauma surgeons all manage severely injured and critically ill patients. "Trauma surgery" isn't really a specialty in the UK with the possible exception of the Royal London (i.e. Barts Centre for Trauma Sciences). You can probably do whatever you want so have a think about your ideal placement and then make it happen rather than feeling you have to apply for opportunities that are advertised.
Stay out of labs if you can unless you are considering a career in translational science. You're likely to spend your whole summer learning techniques that you will never use again and would have to be very lucky to get something tangible (e.g. a research paper) in such a short time. Do something with patients - it's what you signed up for ;-)
And finally, consider doing multiple things with your summer rather than one long commitment.