The stable tree of LilyPond is designated 2.2
Currently officially available in the FreeBSD portstree is 2.0.3. Unfortunately the port does not build, but you may try the 2.2.2 version available here. The FreeBSD port will be updated soon, see http://www.freebsd.org/cgi/query-pr.cgi?pr=67984
The latest available FreeBSD port skeleton is lilypond-2.2.2. Until it is committed into the FreeBSD ports tree, it can be downloaded here, or accessed via the FreeBSD Portrookies project on sourceforge. Here you find a short HowTo access the portrookies repository.
Alternatively the 2.2.2 lilypond portskeleton can be downloaded here: http://foo42.de/distfiles/ports-print-lilypond-2.2.2.tar.gz (md5)Download the port skeleton, remove the old /usr/ports/print/lilypond and untar the ports-print-lilypond-2.2.2.tar.gz in /usr/ports/print/.
Then compile as usual.