Question: I've never played Pandemic, but thinking of getting the Legacy edition. Is it possible to play it without the legacy elements a few times first, and get an experience that is same or similar to that of the regular Pandemic?

Answer: 
In fact, the Legacy rules themselves suggest playing a few games if you aren't familiar with Pandemic.

> 
> IF YOU'VE NEVER PLAYED PANDEMIC...
> 
> 
> We recommend that you play a few games without any of the special
> "Legacy" rules to get a feel for the decisions you will have to make.
> 
> 
> Read this rulebook then play without using the following rules:
> 
> 
> •Game Months, Legacy Deck, Dossiers
> 
> 
> •Objectives, Funding, Game Calendar, Panic Level
> 
> 
> •Scars and Lost Characters
> 
> 
> •Game End Upgrades
> 
> 
> The object of these warm-up games is to cure four diseases before any of
> the game-losing conditions are triggered (noted on page 14 of these rules).
> You should play at least two games this way to get a feel for the game before
> adding the additional rules.
> 
> 
>
Like people said before, it is easy to play vanilla pandemic with the pandemic legacy box. Moreover, various extra components/rules supplied with the game and gradually revealed through the game make it possible to play many interesting modifications of the game even after you finish the campaign.