I don't think so... not via code hinting in the IDE. Because
at design time Flex Builder hasn't actually gone out and polled the
service. Thus it wouldn't know the methods actually available. On
top of which, if you're calling the service via the HTTPService or
URLLoader, those classes are too generic to even recognize at
design time that you're actually accessing a web service (the URL
could, for example, simply be a CSV or XML file).
I think the closest you'd get to an integrated solution is
the SOAPSpy plug-in for Eclipse (so it should work in FlexBuilder
2... but you'd probably have to switch into a different
workspace/view). But I think you'd find a more robust solution in
the stand-alone desktop utility XMLSpy, or the online tools
available at xmethods.com or webservicelist.com.