Can I try the program without any layout connection?

From Jmri

Yes.

If your computer does not have JAVA installed, download and install the latest version of JAVA from Suns Java site.

THEN download and install the JMRI suite from here.

Start the program; set the preferences to "LocoNet Simulator" as a protocol. That's a simulated LocoNet connection which will allow you to play with all of the various capabilities.

Don't forget that the download is free, so there's no economic risk to trying it!