是的，to come along是opportunities的定语，表示主谓关系。可以改为定语从句：

I made a conscious decision not to jump on the first opportunities to come along.

=I made a conscious decision not to jump on the first opportunities that would come along.

come along为短语动词，其意义之一为：

3 : to happen or appear as someone or something that might be used, chosen, etc.

• She says she won't just marry the first man that comes along.

• An opportunity like this doesn't come along [=occur] too often.