Generally, yes. I was at WDW a month ago and we had a 90-minute rainstorm (pretty hard rain). Everyone scattered and ran for cover. We "ponchoed up" and carried on, and had pretty much walk-ons the whole time.
FYI, just because there's rain in the forecast doesn't mean you'll get constant rain. We had rain in our forecast every day for seven days, and only got one fairly brief shower, one day out of seven!