Cannot get rvm to install correctly

Is anyone noticing problems when trying to install rvm on ubuntu? I have both Ruby 1.8.7 and 1.9.2 installed on my machine but can't figure out how to make it default to 1.9.2 other than the rvm route. However, when I go to install rvm using the following command:

bash -s stable < <(curl -s https://raw.github.com/wayneeseguin/rvm/master/binscripts/rvm-installer )

I receive this error message:

Warning: /usr/share/ruby-rvm/archives/wayneeseguin-rvm-stable.tgz: Permission 
Warning: denied
  0  792k    0  2896    0     0   1878      0  0:07:11  0:00:01  0:07:10  128k
curl: (23) Failed writing body (0 != 2896)

Could not download 'https://github.com/wayneeseguin/rvm/tarball/stable'.
  curl returned status '23'.

I looked around for a fix but couldn't locate one. This problem has been bugging me since August.

Any help if much appreciated.

PS. If it is easier to remove 1.8.7, do you suggest I just do that?

Update:

Using sudo apt get.

I almost can't believe what a pain in the a&& it is just to use rvm. After I finally got rvm installed and the bash files working correctly, I went to install ruby version 1.9.2. Of course, the rvm git file has the wrong code as you can read about in this link: https://github.com/wayneeseguin/rvm/commit/52018750763d5321b7b993e201c8589b98e090f9

So here we go again, I opt to use rvm install 1.9.2-head and it installs this version of ruby correctly.

I then tell rvm to use version 1.9.2 with the follow command, rvm use 1.9.2-head. Rvm tells me it is now using 1.9.2. But then when I version check ruby with ruby -v, I find out that it is still using 1.8.7.

Why is it so difficult to get this working? I feel like I've wasted hours on something that should have been relatively easy.