Currently Camino lacks the ability to change page direction or text field direction via any UI (this is important when working in RTL languages on poorly-designed pages or in pages with non-native (e.g., English) UIs.
Fortunately, there are two bookmarklets which can be used as work-arounds:
<textarea> or <input type="text">; thanks to Jesse Ruderman of Squarefree Bookmarklets fame.To use/install, drag the link(s) from this page to Camino’s Bookmark Bar; then click on the bookmarklet in the bar when you need to change directions.