I got a 5071c and I was wondering if I go down to the IRS office. If it will make everything faster to get my refund if I go in person to let them know it's me or just call which is better??

Best way is to contract them and ask about your case and what is needed to be prepared for the refund, then you make an appointment and go there. That's the best way

The letter tells you to call first then if you can't do it with rep over the phone and you can't get it online then make appointment for your local office the process is quick once you verify whatever method is used