Guests are always welcome, with or without prior arrangement, to attend any scheduled activity listed on <a href="http://www.ekoji.org/">this page</a>.
Come as you are - Jodo Shinshu temples are informal. However, if you're curious about what you might expect, here's some information you might find helpful: <a href="http://www.shindharmanet.com/shinbasics/etiquette.htm">Jodo Shinshu Buddhist Etiquette</a>.