According to the 
<a href="http://web1.ncaa.org/web_files/champ_handbooks/lacrosse/2010/10_mlacrosse.pdf">NCAA Men's Lacrosse Championship Handbook</a>
(I lost the link to the 2011 handbook, but it's the same)
<ul>
<li>Pairings for first-round, second-round, quarterfinal and semifinal
games are determined by the geographical proximity of teams.
<li>Once selected, teams will be grouped in clusters according to
natural geographic proximity. Teams will then be paired according to
geographic proximity. A team may be moved to numerically balance the
bracket if geographic proximity is maintained.  Teams should be paired
and eligible sites should be selected according to geographic proximity
(within 500 miles).
<li>Teams may be seeded on a regional basis using the regional selection
criteria.  However, geographic proximity takes precedence over seeding.
<li>Teams from the same conference do not have to play one another in
the first round as long as geographic proximity is maintained.
<li>The highest seeded team that meets all selection criteria will
be selected as the host institution, provided geographic proximity
is maintained.
</ul>
<p>
Team seedings are not released, so
my bracket may not accurately reflect home-visitor team status.
Also, my bracket is computerized, and may need some byes, "phantom"
games, or readjustment to reflect the NCAA bracket.