Check out mediacoder audio edition. Free. Transcodes straight from flac to mp3. Very easy to use. It's so easy to use that you can basically decide spur of the moment what you want to convert, do it quickly, and put the mp3s whereever you need them. I would suggest something in the range of 192 VBR.
MP3 conversion rate suggestions
I'm in the process of converting my FLAC files to MP3's for use on my iPhone. I will be using LAME. What have you found to be the best rate type (VBR, CBR etc.), & rate setting? That is, what saves the most memory, but provides the most acceptable sonics?