I have been working at Port of Los Angeles part-time (More than a year)
-A lot of opportunities
-Work can be slow sometimes
I applied through other source. I interviewed at Port of Los Angeles (Wilmington, CA).
Started as a part timer in the city, before sitting to take the gardening exam. Scored high enough to be reachable and was certed by the Harbor Department.
If you need study material for the exam try using the Sunset Western Gardener Book. Make sure you know the basics of horticulture (NPK, Photosynthesis, plant anatomy, etc), LA native plants, drought tolerant plants, IPM practices for pest (such as soap & water or lady bugs for mildew or aphids). PPE is big so know it from head to toe Hard hat(cap), eye/ear protections, gloves, chaps(chainsaws or hedger trimmers) and stell toe boots.
Make sure you know ATLEAST five annuals and five perennials plants by their common name. Also study the basic anatomy of an irrigation system from sprinkler head to valve box.