Sure you can but it will still redirect to https try this bellow under your sslvpn attributes
asa5500fw(config)# group-policy attributes
asa5500fw(config-group-policy)# http redirect outside http
see details on http redirect
http://www.cisco.com/en/US/docs/security/asa/asa80/command/reference/gh.html#wp1760826
then try http://asa_outside_ip
it should redirect to https
Regards
Jorge Rodriguez