a kiss is a very tender and personal emotion. sometimes emotions do get outburst, you just cant control them. i think that its important to express your emotions, ur love. when u feel like kissing...please go ahead and kiss; be it a public or a private place.
however, if u have planned a kiss, please do it in private coz it may feel akward to ur partner or the public when u do it in open. it is also termed by some people as PDA "Public Display of Affection"