Since you will be predominantly diving in the US, stick with imperial units if for no other reason it's what most of your buddies will be using so it makes communication a lot easier. If you go to a dive spot where metric is the standard, it helps to have an SPG like the OMS units that read in both imperial and metric for easier communication and (more importantly, IMO) less stress underwater from doing a bunch of math in my head.
It is still a good idea to learn how to work in both systems and learn the conversions between them. A few months ago I had the opportunity to dive locally with a diver who was visiting from Russia. Between my gear that is fairly bilingual and the fact that I can do some of the basic conversions we decided on using Metric for communicating gas status, since her SPG was metric only. If I wanted to know what she had in imperial, I simply had to look at my SPG.
It also helps in that situation to have a good dive plan with mutually agreed-upon numbers before getting in the water. In the example above, we did exactly that and the dive went incredibly smooth; better than many dives I have with the local divers around here.
To Recap:
Learn both systems and to convert between them (at least the basics)
If possible utilize equipment that reads in boths systems
Plan your dive and dive your plan.
Peace,
Greg