No, its catchrate is rather low as for most other legendaries. However if you fail to catch it you are able to try it again as Keldeo will re-appear in the same location again.
Unfortunetaly the game can have issues when using mobile data. I would suggest to use WIFI instead or try to use a VPN. Both options should fix the problem you are experiencing.
Super cool art, great service and easy contact. Really recommended if you are looking for a forum signature.
Thanks for the awsome signature and the profile picture.