Well if your meter is one that measures true RMS values, then reading it as a DC milliamp current will give you the correct answer. However most inexpensive digital multi-meters don't have that feature so you will get a reading but it won't be an accurate measurement. You can easily calculate the average current flow by multiplying the 100% current flow value by the % duty cycle that the pwm signal is outputting. That is (output pwm value / 255) X full on current value.
Lefty