How do you say baby when are you coming to visit me?

Not exactly sure who this person is that you are referring to as "baby," but hopefully this answers your inquiry.

Romantic relationships: (spouse, etc..)

mi amor, cuando vienes a visitar?

--"My love, when will you visit me?"

There a tons of ways to express endearment in Spanish:

(just add the, "cuando vienes a visitar?")

• Cariño: honey/dear (affectionate)
• Mi cielo: my heaven
• Mi corazón: my heart
• Mi querido - my dear
• Mi angél - my angel
• Guapo or guapito - handsome
• Lindo - cute/cutie
• Mi vida - my life
• Mi rey - my king
• Bello - beautiful

Friends/Family:

muneca preciOSa, cuando vienes a visitar?

--"Precious/doll/ beautiful, when will you visit me?"

Alternative ways to say the same phrase:

cuándo vendrás para acá?

cuándo vas a venir para acá?

--"when are you coming over?"

cuándo vienes aqui?

cuándo vengas aquí?

--"when are you coming here?"

estoy viniendo visitar pronto

--"I will visit soon"

cuando puedes vienes a visitar?

--"when will you visit me?"

Y. Suzuki

(yes, i'm not Spanish. Yo soy Japones)