For those who aren’t familiar with letterbox hybrid caches, they are just like traditional caches, but they included a stamp with the log book. Find the cache just like normal, break out your own stamp (if you have one), stamp the log book, and use the letterbox stamp in the cache container to stamp your own log book (if you have one). The stamp is self-inking. If you don't have a letterbox stamp, you're welcome to just sign the log book as you would in a traditional cache. Make sure to leave the stamp in the letterbox container!
NOTE: There is a gully separating letterboxes #01 – #08 from letterboxes #09 – #12. The best way to access letterboxes #01 – #08 is from Derrington Road, which is gravel, narrow, and bumpy, but even small cars can make it to the reservoir area without any trouble (from there you’ll need to judge if you want to drive around the reservoir or hike, bike, etc.). For those who like to hike/bike (we do), you can park at the reservoir entrance and do them all by bike after getting the first one along the way. The best way to access letterboxes #09 – #12 is from the Fallbrook Drive side of the gully.
The usual cautions exist out here: snakes, insects, spiders, poisonous plants, etc., but the caches are all pretty easy to access. The containers vary. Enjoy!