This cache is available during daylight hours ONLY and is courtesy of the open placement park list by the Fairfax County Park Authority. You can check the list of approved parks here: http://www.fairfaxcounty.gov/parks/geocaching.htm
From Wikipedia: The Caesar cipher is named after Julius Caesar, who, according to Suetonius, used it with a left shift of three to protect messages of military significance. If he had anything confidential to say, he wrote it in cipher, that is, by so changing the order of the letters of the alphabet, that not a word could be made out.
Even if you do not know the number of digits that are shifted, the cipher can be "Brutus" forced by picking a short part of the message and trying out different numbers for the shift. You can shorten the search by making an educated guess by looking for a familiar pattern in a word (like repeating characters that would represent double letters in the decoded text) and figuring out the shift needed to change the cipher text to the right letters. Some on-line resources will even take your cipher text and display multiple shifts.
The cipher text below also has been split at a different place to make it more difficult to detect the starting point.
MRXJSYV IMKLXRM RIQMRYX IWPIEZI RSWXSRI YRXYVRI HRSVXLX LMVXCIM KLXHIKV IIWJMJC TSMRXWM BLYRHVI HIPIZIR QMRYXIW AIWXDIV SWIZIRX CWIZIRH IKVIIWI PIZIRTS
NOTICE: Please be respectful of the posted park hours. If you enter the park after hours you are trespassing. If you are stopped you can be ticketed or arrested and will put the future of geocaching in the parks in jeopardy.
(Note -- background image is not relevant for completing this task.)