From a quick look it seems like phonegap is used for making appStore apps. I was thinking of building a mobile web browser app. That's why I was looking at Sencha, which apparently uses phonegap to access data on the phone. http://www.sencha.com/learn/Tutorial:A_Sencha_Touch_MVC_appl...
First, I'm not an immigration lawyer so don't take my advice.
However, I've been through a lot before I got my green-card and very familiar with the process.
Coming here as a tourist and working (even for a Russian company) is illegal. even if you come here just for a tech conference without working, it's considered a business trip. bottom line, you have to declare you are here on a business trip cause they will check your laptop, go though your emails, find out you are performing some work for a US entity and deny your entrance and take away your visa.
Definitely, not something I would recommend.
Vladimir, I'm not sure if what is your visa situation, but getting a work visa in the US is very hard and takes a lot of time and effort.
I would start researching it right away and collecting your documents (degrees, awards, letters of reference, etc...). If you just want to come visit, you won't be able to work here with a tourist visa so start looking into it.
Good luck.