Having a community garden plot myself, so I gotta ask this.
Is your plot open? That is side by side with another plot or is it separated from other plots by walkways?
Is there open access? Is the garden fenced or gated?
Read the community garden rules. You may have height limitations and some plants may not be allowed. There may also be attendance and annual requirements. if there is open access, you will find that some of your vegetables will be harvested for you.
Depending on how much time you actually have to spend at the garden, think about planting things that are disease resistant, don't need to have a lot of attention and a little unusual. Community gardens with so many plants and part time gardeners around are often magnets for pests and diseases.
Tomatoes do not grow well at my community garden so very few people even try to plant it anymore. If they did tomatoes would probably be high on the theft lists. Here it is best to have just a few plants and not rows of the same plant. Thieves want to pick up 20 cabbages, not just one. Beans, cucumbers and plants that people know and are very common are often taken.
Plants that get stolen the most here are bananas, cabbages, squash, and eggplant. Some ethnic plants are regularly raided like bitter melon, moringa, chayote, sweet potatoes, and Alucon (birch tree).
No one has yet reported any thefts of kale, kohlrabi, radicchio, or the more unusual vegetables.
Community gardens are a great place to make friends and learn how to grow different things and learn about different gardening practices. A 4x6 garden plot will not take up that much of your time, and if your garden allows it, you can arrange with other gardeners to schedule yourselves so you can help keep an eye out for each other.
P.S. Make sure you take your tools home. Make simple supports. Timers are not allowed at my garden.
With such a small plot, I'd plant some herbs and short plants with good disease resistance. I'd try some unusual plants that people won't recognize too easily like edible flowers (nasturtiums, daylily), spinach substitutes (amaranth, NZ spinach), Jerusalem artichoke, Jicama. It would be a great opportunity to expand your culinary horizons.
Happy gardening in Hawaii. Gardens are where people grow.