IMO, it would be in your team's best interest to do so. That way you can precoordinate the alliance and share scouting data for a potentially stronger alliance (your team's 2nd pick). This, however, is assuming that the team you contacted is interested.
By doing so you can also root out teams that are not interested in an alliance. It saves time and additionally prevents the slight embarrassment of being declined upon
(that is, if they are within the top 8).