"resistor voltage divider ", No. Voltage out will vary with the current being drawn.
You don't have a lot of current need there, just use a LM7812 to bring the 28V down to 12V.
Will be dissipating 2.4W (28V - 12V) * 0.15A, so a heatsink will likely be needed.
I use this boost regulator in my fencing scoring machine, has worked out very well.http://www.pololu.com/catalog/product/799
Supply it with 5V (4A capable), adjust the output for 12V.
Drives 2 banks of 20 LEDs, MOSFET speaker amplifier, and 2 remote boxes 50 feet away where the 12V drives 2 more banks of LEDs in each box, and a 7805 to make power for a promini that controls the transistors for the LEDs.