I just got a text from +19086691405 sayng "Hi :P"...I asked who it is, and got a reply saying "Let's talk on ya-hoo...add me sophiewoman36"...what the hell is this?

I just got a text from sophiewoman36 at 270--775-4106.  Also not stating a name.  But insisting I add her and saying "Can you remember who I am??  Add me to refresh your memory.

I too just received a text from this number stating "hi !!".  
Don't reply.  Don't touch this. Simply delete.  This is a phishing scan to work their way to getting data on you.  Perhaps passwords, PINs, etc.

Literally JUST got a text from this number asking to add a Y! messenger screen name of ryanflirty, then when I asked who it was, they said they have no signal. Now I'm all sorts of paranoid.

I received a text from 352-389-4512. The message was, "Hi ;-)" When asked who they were, the response was a yahoo screen name of sophiewoman36. When asked again who they were, the response was "sry I have no reception :-("

This number texted me also and asked me to add them to yahoo.  When I said I do not have it, they said they didn't have good reception.

Someone texted me from this number as well...and never texted back after I asked who this was

This number texted me and then sent me a yahoo messenger ID. Might be spam might be some pedophile or something not really sure but seemed really sketchy.