You have 2 independent variables but you are interested only in checking the continuous variable? Does that mean you only have 1 independent variable? It's abit confusing the way you have described the problem! Regarding the logistic regression produced using Fit Y by X, its strange that you only have a plot. Under the plot there ought to be an outline called Whole Model Test which gives you the test results to assess whether the model is statistically significant. What version of JMP are you using?

-Dave