Udaipur is easily accessed by road (from Jaisalmer, Jodhpur and Pushkar), by train (from Delhi, and many other Indian cities), and by air (from Mumbai, Delhi, Jaipur and Jodhpur).
On the way to or from Udaipur, I recommend a visit to some of the nearby attractions. One of the nicest is Nagda, a small town 23 Km Northwest of Udaipur, where you will find the Sas Bahu Temple complex.