Head to Monument Park, and observe border marker #1 cairn on the US-Canada border. Take the sometimes steep trail down to the beach and look for the cache. There is room for tradables etc. Happy caching!
From PointRobertsTourism.com:
The small park overlooks the Strait of Georgia from its perch among the trees atop a small bluff. An easy walking trail follows the top of the vegetation-covered slope, then descends through a forest of giant old Douglas fir trees to a picturesque beach. There are no facilities and no day fee at Monument Park.
Monument Park is located at the Northwest corner of Point Roberts. The park is named after the granite obelisk, Border Marker Number One, that stands at the entrance to the park. This monument to the 49 parallel was fabricated in Scotland and New Westminster in 1861 and sits at the most western point in the northern Canadian - US border.