Cache is not at the posted coordinates, but you do need to go there.
Use the park rules sign near the posted coordinates to solve for the final:
N42 46.ABC W 086 01.XYZ
A = # of letters in 3rd word of first line (line in black)
B = # of U's on second line
C = # of letters in 3rd word of third line
X = Park closed from 11pm to Xam
Y = # of letters in the last word of first line (line in black)
Z = # of letters in 1st word of 2nd line
Checksum = 29