If you're new to the gardening world or just want to find out about more plants that fit your climate zone, Sunset has launched their online Plant Finder Tool. The free service is essentially an online version of the classic Sunset Western Garden Guide and is a whole database of plants organized by water/sun/climate needs. As has been mentioned in other posts, putting a plant in a spot where it gets the right kind of sun exposure and water is at least half the battle of keeping it alive. Plus, when we did our search, it reminded us that we want to plant some sweet peas:
Searching by zone 21 (Pasadena) we found different succulents, vines and perennials and came up with hundreds of possibilities but were most excited for sweet peas! Fragrant, delicate and they take full sun. We remember growing them from seed when we were little and collecting the blooms into beautiful little bouquets.
You can limit your search to just succulents or just full sun plants to pinpoint exactly what plant is going to fit into that balcony. If you know you're bad at remembering to water or that you don't really get any direct sun in your place, this tool will help you figure out what is likely to survive. Plus it gives you the Latin name and the common name so it's easy to go to the nursery and get what you want.